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{{Short description|2001 Islamist terror attacks in the United States}}
{{For|other attacks on the same date|September 11 attacks (disambiguation)}}
{{Redirect2|Nine eleven|9/11|the calendar date|September 11|the reverse|11/9 (disambiguation)|and|November 9|other uses|911 (disambiguation)}}
{{Redirect|9-11|the collection of interviews with Noam Chomsky|9-11 (book){{!}}''9-11'' (book)}}
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{{Good article}}
{{Use American English|date=July 2021}}
{{Use mdy dates|date=September 2024}}
{{Infobox civilian attack
|title = September 11 attacks
|image_size = 250px
|image = September 11 Photo Montage.jpg <!--Do NOT change a photo without discussion first on the talk page.-->
|alt = A montage of eight images depicting, from top to bottom, the World Trade Center towers burning, the collapsed section of the Pentagon, the impact explosion in the South Tower, a rescue worker standing in front of rubble of the collapsed towers, an excavator unearthing a smashed jet engine, three frames of video depicting American Airlines Flight 77 hitting the Pentagon
|caption = {{unbulleted list|style=white-space:nowrap; |{{longitem|''Top row:'' The Twin Towers of the<br />[[World Trade Center (1973–2001)|World Trade Center]] burning}}|{{longitem|''2nd row, left to right:'' Collapsed section of<br />[[the Pentagon]]; [[United Airlines Flight 175|Flight 175]] crashes into 2 WTC}}|{{longitem|''3rd row, left to right:'' A firefighter requests<br />assistance at [[World Trade Center site]];<br />An engine from [[United Airlines Flight 93|Flight 93]] is recovered}} |{{longitem|''Bottom row:'' [[American Airlines Flight 77|Flight 77]]'s collision with the<br />Pentagon as captured by three<br />consecutive [[Closed-circuit television|CCTV]] frames}}}}
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| location = 
* [[Lower Manhattan]], New York
* [[Arlington County, Virginia|Arlington County]], Virginia
* [[Stonycreek Township, Somerset County, Pennsylvania|Stonycreek Township]], Pennsylvania{{efn|Other, secondary attack locations include the airspaces of [[Massachusetts]], [[New Jersey]], [[Ohio]], [[Kentucky]] and [[West Virginia]].}}
| date = {{start date and age|2001|09|11}}
| time-begin = {{circa|08:13&nbsp;am{{efn|The hijackers began their first attack at around 08:13{{nbsp}}am, when a group of five took control of [[American Airlines Flight 11]], injuring two people and murdering one before forcing their way into the cockpit.}}|lk=no}}
| time-end = 10:03&nbsp;am{{efn|The [[United Airlines Flight 93|fourth and final hijacked plane]] of the attacks crashed in a Pennsylvania field at 10:03{{nbsp}}am, which concluded the attacks since all the attackers were now dead and all of the hijacked planes were destroyed. However, the attackers' damage continued as the North Tower kept burning for an additional 25 minutes until it ultimately collapsed by 10:28 am}}
| timezone = [[Eastern Time Zone|EDT]]
| type = [[Islamic terrorism]], [[aircraft hijacking]], [[suicide attack]], [[mass murder]]
| target = 
* [[World Trade Center (1973–2001)|World Trade Center]] ([[American Airlines Flight 11|AA 11]] and [[United Airlines Flight 175|UA 175]])
* [[The Pentagon]] ([[American Airlines Flight 77|AA 77]]) 
* [[United States Capitol|U.S. Capitol Building]] or the [[White House]] ([[United Airlines Flight 93|UA 93]]; unsuccessful due to [[United Airlines Flight 93#Passenger revolt|passenger revolt]])
| fatalities = [[Casualties of the September 11 attacks|2,996]]{{efn|Thousands more are thought to have died of illnesses related to the attack;<ref>{{cite news |url= https://amp.cnn.com/cnn/2023/09/11/us/new-york-firefighters-911-illness-death |title= First responder deaths from post-9/11 illnesses nearly equals number of firefighters who died that day}}</ref><ref>{{cite web |url= https://www.asbestos.com/featured-stories/9-11-lingering-health-effects/#:~:text=The%20toxic%20cloud%20of%20dangerous,1%2C366%20died%20from%20related%20cancers. |title= 20 Years Later: The Lingering Health Effects of 9/11}}</ref> however, the exact number is unknown as it is difficult to determine whether or not the illnesses were related or unrelated to the attack.}}<br />([[Lists of victims of the September 11 attacks|2,977 victims]] and [[Hijackers in the September 11 attacks|19 Al-Qaeda terrorists]])
| injuries = 6,000–25,000+{{efn| Sources vary regarding the number of injuries―some say 6,000<ref>{{cite web|title=A Day of Remembrance|date=September 11, 2022|url=https://ge.usembassy.gov/a-day-of-remembrance/|publisher=U.S. Embassy in Georgia|access-date=October 27, 2022|archive-date=October 24, 2023|archive-url=https://web.archive.org/web/20231024074052/https://ge.usembassy.gov/a-day-of-remembrance/|url-status=live}}</ref> while others go as high as 25,000.<ref>{{Cite news|last=Stempel|first=Jonathan|title=Accused 9/11 mastermind open to role in victims' lawsuit if not executed|url=https://www.reuters.com/article/us-usa-sept-11-saudi-ksmohammed/accused-9-11-mastermind-open-to-role-in-victims-lawsuit-if-not-executed-idUSKCN1UO27M|access-date=October 27, 2022|publisher=[[Reuters]]|date=July 29, 2019|language=en|archive-date=April 5, 2020|archive-url=https://web.archive.org/web/20200405122413/https://www.reuters.com/article/us-usa-sept-11-saudi-ksmohammed/accused-9-11-mastermind-open-to-role-in-victims-lawsuit-if-not-executed-idUSKCN1UO27M|url-status=live}}</ref>}}
| perps = [[Al-Qaeda]] led by [[Osama bin Laden]] (see also: [[Responsibility for the September 11 attacks|responsibility]])
| partof = [[terrorism in the United States]] <!-- Please discuss at talk page before releasing these words back into the article: "and the [[war on terror]]" -->
| numparts = [[Hijackers in the September 11 attacks|19]]
| motive = Several; see [[Motives for the September 11 attacks]] and [[Fatwas of Osama bin Laden]]
| convicted = {{unbulleted list|[[Zacarias Moussaoui]]|[[Abu Dahdah|Imad Yarkas]]|[[Mounir el-Motassadeq]] (see also: [[Trials related to the September 11 attacks]])}}
| website = 
| notes = 
}}
{{September 11th attacks}}
{{Campaignbox al-Qaeda attacks}}
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The '''September 11 attacks''',{{efn|Al-Qaeda's name for the events is the '''Manhattan Raid''', though this name is rarely used by non-jihadist sources.<ref>{{Cite web | url=https://www.brookings.edu/articles/al-qaedas-911-obsession/ | title=Al Qaeda’s 9/11 Obsession | first=Bruce | last=Riedel | date=2011-07-15 | website=www.brookings.edu}}</ref>}} commonly known as '''9/11''',{{efn|The expression ''9/11'' is typically pronounced "nine eleven" in English,<ref>{{cite book |last1=Allan |first1=Keith |author-link1=Keith Allan (linguist) |last2=Burridge |first2=Kate |author-link2=Kate Burridge |year=2006 |title=Forbidden Words: Taboo and the Censoring of Language |publisher=[[Cambridge University Press]] |location=Cambridge |isbn=978-1-139-45760-6 |url={{google books|plainurl=y|id=b2rCLYHjDMgC}} |page=233 }}</ref> even in places that use the opposite date format. The slash is not pronounced.}}  were four coordinated [[Islamist terrorist]] suicide attacks carried out by [[al-Qaeda]] against the United States in 2001. On that morning, [[Hijackers in the September 11 attacks#Hijackers|19 terrorists]] hijacked four commercial airliners scheduled to travel from the [[East Coast of the United States|East Coast]] to California. The first two teams of hijackers crashed the first two planes into the Twin Towers of the [[World Trade Center (1973–2001)|World Trade Center]] in New York City, while the remaining hijackers aimed the next two flights toward targets in or near Washington, D.C., in an attack on the nation's capital. The third team succeeded in striking [[the Pentagon]], the headquarters of the [[U.S. Department of Defense]] in [[Arlington County, Virginia]], while the [[United Airlines Flight 93|fourth plane]] hijacked by the fourth team crashed in rural [[Pennsylvania]] during a passenger revolt. The September 11 attacks killed 2,977 people, making it the deadliest terrorist attack in history. In response to the attacks, the United States waged the multi-decade global [[war on terror]] to eliminate hostile groups deemed terrorist organizations, as well as the foreign governments purported to support them, in [[Islamic Emirate of Afghanistan (1996–2001)|Afghanistan]], [[Ba'athist Iraq|Iraq]], [[Syria]], and several other countries.

Ringleader [[Mohamed Atta]] flew [[American Airlines Flight 11]] into the [[List of tenants in 1 World Trade Center (1971–2001)|North Tower]] of the World Trade Center complex in [[Lower Manhattan]] at 8:46&nbsp;a.m.{{efn|name=Time4|The exact time is disputed. The ''[[9/11 Commission Report]]'' states that Flight 11 struck the North Tower at 08:46:40&nbsp;am,<ref>{{cite web |work=9/11 Final Report of the National Commission |title=Collapse of WTC1 |year=2004 |url=https://9-11commission.gov/report/911Report.pdf |page=24 |access-date=December 7, 2023 |archive-date=September 12, 2017 |archive-url=https://web.archive.org/web/20170912055527/https://9-11commission.gov/report/911Report.pdf |url-status=live }}</ref> NIST reports 08:46:30&nbsp;am,<ref>{{cite journal |last=National Institute of Standards and Technology |title=Final report on the collapse of the World Trade Center |journal=NIST |year=2005 |url=https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1.pdf |page=69 |access-date=December 7, 2023 |archive-date=July 7, 2021 |archive-url=https://web.archive.org/web/20210707002217/https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1.pdf |url-status=live }}</ref> and some other sources claim 08:46:26&nbsp;am.<ref name="102mins">{{cite news|date=May 26, 2002|title=102 Minutes: Last Words at the Trade Center; Fighting to Live as the Towers Die|work=The New York Times|url=https://www.nytimes.com/2002/05/26/nyregion/102-minutes-last-words-at-the-trade-center-fighting-to-live-as-the-towers-die.html|access-date=June 23, 2023|archive-date=September 12, 2009|archive-url=https://web.archive.org/web/20090912025748/http://www.nytimes.com/2002/05/26/nyregion/102-minutes-last-words-at-the-trade-center-fighting-to-live-as-the-towers-die.html|url-status=live}}</ref>}} Seventeen minutes later, at 9:03,{{efn|name=Time|The exact time is disputed. The ''9/11 Commission Report'' states that Flight 175 struck the South Tower at 09:03:11&nbsp;am,<ref>{{cite report |title=Final Report of the 9/11 Commission on Terrorist Attacks Upon the United States |date=July 22, 2004 |publisher=National Commission on Terrorist Attacks Upon the United States |access-date=August 15, 2021 |url=https://9-11commission.gov/report/911Report.pdf |ref={{harvid|9/11 Commission|2004a}} |archive-date=August 16, 2021 |archive-url=https://web.archive.org/web/20210816164111/https://www.9-11commission.gov/report/911Report.pdf |url-status=live |pages=7–8}}</ref><ref>{{cite report |title=Staff Report of the 9/11 Commission on Terrorist Attacks upon the United States |date=September 2005 |orig-date=August 26, 2004 |publisher=National Commission on Terrorist Attacks Upon the United States |access-date=August 15, 2021 |url=https://www.archives.gov/research/9-11/staff-report-sept2005.pdf |ref={{harvid|9/11 Commission|2004b}}|archive-date=July 12, 2014 |archive-url=https://web.archive.org/web/20140712075041/http://www.archives.gov/research/9-11/staff-report-sept2005.pdf |url-status=live |page=24}}</ref> NIST reports 09:02:59&nbsp;am,<ref>{{cite report |title=Visual Evidence, Damage Estimates, and Timeline Analysis |author=Building and Fire Research Laboratory |publisher=National Institute of Standards and Technology, United States Department of Commerce |date=September 2005 |url=https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf |ref={{harvid|NISTb|2005}} |access-date=August 24, 2021|archive-date=September 11, 2021 |archive-url=https://web.archive.org/web/20210911011051/https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf |url-status=live |page=27}}</ref> and some other sources claim 09:03:02&nbsp;am.<ref>{{cite news |title=Timeline for United Airlines Flight 175 |url=https://www.npr.org/templates/story/story.php?storyId=1962517 |publisher=NPR |date=June 17, 2004|language=en |access-date=August 24, 2021 |archive-date=August 24, 2021 |archive-url=https://web.archive.org/web/20210824221736/https://www.npr.org/templates/story/story.php?storyId=1962517 |url-status=live }}</ref> In any case, the 16-minute gap between each impact is rounded to 17.{{sfn|9/11 Commission|2004a|p=302}}}} the [[List of tenants in 2 World Trade Center|South Tower]] was hit by [[United Airlines Flight 175]]. Both [[Collapse of the World Trade Center|110-story skyscrapers collapsed]] within an hour and forty-one minutes,{{efn|name=Time1|While NIST and the 9/11 Commission give differing accounts of the exact second of the North Tower's collapse initiation, with NIST placing it at 10:28:22&nbsp;am.<ref>{{cite web|url=https://6abc.com/what-happened-on-911-september-11-remembrance-timeline-facts-about-911/6411796/|title=9/11/01 timeline: How the September 11, 2001 attacks unfolded|publisher=[[WPVI-TV]]|language=en-US|url-status=live|date=September 11, 2023|access-date=November 4, 2023|archive-date=November 5, 2023|archive-url=https://archive.today/20231105012442/https://6abc.com/what-happened-on-911-september-11-remembrance-timeline-facts-about-911/6411796/}}</ref><ref>{{cite journal |last=National Institute of Standards and Technology |title=Final report on the collapse of the World Trade Center |journal=NIST |year=2005 |url=https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1.pdf |page=229 |access-date=December 7, 2023 |archive-date=July 7, 2021 |archive-url=https://web.archive.org/web/20210707002217/https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1.pdf |url-status=live }}</ref> and the commission at 10:28:25&nbsp;am,<ref>{{cite web |work=9/11 Final Report of the National Commission |title=Collapse of WTC1 |year=2004 |url=https://9-11commission.gov/report/911Report.pdf |page=329 |access-date=December 7, 2023 |archive-date=September 12, 2017 |archive-url=https://web.archive.org/web/20170912055527/https://9-11commission.gov/report/911Report.pdf |url-status=live }}</ref> it is generally accepted that Flight 11 did not strike the North Tower any sooner than 8:46:26&nbsp;am,<ref name="102mins"/> so the time it took for the North Tower to collapse was just shy of 102 minutes either way.}} bringing about the destruction of the remaining five structures in the WTC complex and damaging or destroying nearby buildings. [[American Airlines Flight 77]] flew towards Washington, D.C. and crashed into the Pentagon at 9:37&nbsp;a.m., causing a partial collapse. The fourth and final flight, [[United Airlines Flight 93]], also changed course towards Washington, believed by investigators to target either the [[United States Capitol]] or the [[White House]]. Alerted to the previous attacks, the passengers revolted against the hijackers who then crashed the aircraft into a [[Stonycreek Township, Somerset County, Pennsylvania|Stonycreek Township]] field, near [[Shanksville, Pennsylvania]], at 10:03&nbsp;am. The [[Federal Aviation Administration]] ordered an indefinite [[ground stop]] for all air traffic in U.S. airspace at 9:45&nbsp;am (59 minutes following the first impact), preventing any further aircraft departures until September 13 and requiring all airborne aircraft to return to their point of origin or divert to Canada. The actions undertaken in Canada to support incoming aircraft and their occupants were collectively titled [[Operation Yellow Ribbon]].

That evening, the [[Central Intelligence Agency]] informed [[POTUS|President]] [[George W. Bush]] that its [[Counterterrorism Mission Center|Counterterrorism Center]] had identified the attacks as having been the work of Al-Qaeda under [[Osama bin Laden]]. The United States formally [[U.S. government response to the September 11 attacks|responded]] by launching the [[war on terror]] and [[United States invasion of Afghanistan|invading Afghanistan]] to depose the [[Taliban]], which rejected the conditions of U.S. terms to expel Al-Qaeda from Afghanistan and extradite its leaders. The U.S.'s invocation of [[North Atlantic Treaty#Article 5|Article 5 of the North Atlantic Treaty]]—its only usage to date—called upon allies to fight Al-Qaeda. As U.S. and [[NATO]] invasion forces swept through Afghanistan, bin Laden [[Battle of Tora Bora|eluded them]] by disappearing into the [[Spīn Ghar|White Mountains]]. He denied any involvement [[2004 Osama bin Laden video|until 2004]], when excerpts of a taped statement in which he accepted [[Responsibility for the September 11 attacks|responsibility for the attacks]] were released. Al-Qaeda's cited [[Motives for the September 11 attacks|motivations]] included [[Israel–United States relations|U.S. support of Israel]], the presence of [[Operation Southern Watch|U.S. military bases in Saudi Arabia]] and [[sanctions against Iraq]]. The nearly decade-long [[Manhunt for Osama bin Laden|manhunt for bin Laden]] concluded on May 2, 2011, when [[Killing of Osama bin Laden|he was killed during a U.S. military raid]] on [[Osama bin Laden's compound in Abbottabad|his compound]] in [[Abbottabad, Pakistan]]. The [[War in Afghanistan (2001–2021)|war in Afghanistan]] continued for another eight years until the agreement was made in February 2020 for American and NATO troops to [[Withdrawal of United States troops from Afghanistan (2020–2021)|withdraw from the country]]. The last members of the U.S. armed forces left the region on August 30, 2021, after which the Taliban rapidly returned to power. [[Ayman al-Zawahiri]], another planner of the attacks who succeeded bin Laden as leader of Al-Qaeda, was [[Killing of Ayman al-Zawahiri|killed by U.S. drone strikes]] in [[Kabul]], Afghanistan, on July 31, 2022.<ref name="The New York Times">{{Cite news |last1=Baker |first1=Peter |last2=Cooper |first2=Helene |last3=Barnes |first3=Julian |last4=Schmitt |first4=Eric |date=August 1, 2022 |title=U.S. Drone Strike Kills Ayman al-Zawahri, Top Qaeda Leader |work=The New York Times |url=https://www.nytimes.com/2022/08/01/us/politics/al-qaeda-strike-afghanistan.html |url-status=live |access-date=August 1, 2022 |archive-url=https://web.archive.org/web/20220801215209/https://www.nytimes.com/2022/08/01/us/politics/al-qaeda-strike-afghanistan.html |archive-date=August 1, 2022}}</ref>

Excluding the hijackers, the attacks [[Casualties of the September 11 attacks|killed 2,977 people, injured thousands more]] and gave rise to [[Health effects arising from the September 11 attacks|substantial long-term health consequences]] while also causing at least $10{{spaces}}billion in infrastructure and property damage. It remains the deadliest terrorist attack in history as well as the deadliest incident for [[List of the deadliest firefighter disasters in the United States|firefighters]] and [[List of law enforcement officers killed in the line of duty in the United States|law enforcement]] personnel in American history, killing 343 and 72 members, respectively. The loss of life stemming from the impact of Flight 11 made it [[List of deadliest aircraft accidents and incidents#Table|the most lethal multi-plane crash in aviation history]] followed by the death toll incurred by Flight 175. The destruction of the World Trade Center and its environs seriously harmed the U.S. economy and [[Economic effects of the September 11 attacks|induced global market shocks]]. Many other countries strengthened [[anti-terrorism legislation]] and expanded their powers of [[Law enforcement agency|law enforcement]] and [[Intelligence agency|intelligence agencies]]. The total number of deaths caused by the attacks, combined with the death tolls from the conflicts they directly incited, has been estimated by the [[Costs of War Project]] to be over 4.5&nbsp;million.<ref name=":2">{{Cite web |date=May 15, 2023 |title=Post-9/11 wars have contributed to some 4.5 million deaths, report suggests |url=https://www.washingtonpost.com/world/2023/05/15/war-on-terror-911-deaths-afghanistan-iraq/ |access-date=May 26, 2024 |last=Berger |first=Miriam |website=The Washington Post |archive-date=May 29, 2023 |archive-url=https://web.archive.org/web/20230529144019/https://www.washingtonpost.com/world/2023/05/15/war-on-terror-911-deaths-afghanistan-iraq/ |url-status=live |url-access=subscription}}</ref> Cleanup of the [[World Trade Center site]] (colloquially "Ground Zero") took eight months and was completed in May 2002, while the Pentagon was repaired within a year. After delays in the design of a replacement complex, [[World Trade Center (2001–present)|six new buildings]] were planned to replace the lost towers, along with a museum and memorial dedicated to those who were killed or injured in the attacks. The tallest building, [[One World Trade Center]], began construction in November 2006; it opened in November 2014. [[Memorials and services for the September 11 attacks|Memorials to the attacks]] include the [[National September 11 Memorial & Museum]] in New York City, the [[Pentagon Memorial]] in Arlington County, Virginia, and the [[Flight 93 National Memorial]] at the Pennsylvania crash site.

== Background ==
{{anchor|Al-Qaeda}}{{Further|Fatwas of Osama bin Laden|Political views of Osama bin Laden|1993 World Trade Center bombing}}

In 1996, [[Osama bin Laden]] of the Islamist militant organization [[Al-Qaeda]] issued his first ''[[Fatwa|fatwā]]'', which declared war against the United States and demanded the expulsion of all American soldiers from the [[Arabian Peninsula]].<ref>{{cite news |title=Bin Laden's fatwā (1996) |url=https://www.pbs.org/newshour/terrorism/international/fatwa_1996.html |url-status=dead |publisher=PBS |access-date=May 29, 2014 |archive-url=https://web.archive.org/web/20011031024057/http://www.pbs.org/newshour/terrorism/international/fatwa_1996.html |archive-date=October 31, 2001}}</ref> In a second 1998 ''fatwā'', bin Laden outlined his objections to [[Foreign policy of the United States|American foreign policy]] with respect to [[Israel]], as well as the continued presence of American troops in Saudi Arabia after the [[Gulf War]].<ref name="PBS 2013-11-28">{{cite news |url=https://www.pbs.org/newshour/updates/military-jan-june98-fatwa_1998/ |archive-url=https://web.archive.org/web/20131128194258/http://www.pbs.org/newshour/updates/military/jan-june98/fatwa_1998.html|archive-date=November 28, 2013 |title=Al Qaeda's Second Fatwa |website=[[PBS NewsHour]] |publisher=[[PBS]] |url-status=live |access-date=May 29, 2014}}</ref> Bin Laden maintained that [[Muslims]] are obliged to attack American targets until the aggressive policies of the U.S. against Muslims were reversed.<ref name="PBS 2013-11-28" /><ref>{{cite book|last=Logevall|first=Fredrik|title=Terrorism and 9/11: A Reader|publisher=Houghton Mifflin Company|year=2002|isbn=0-618-25535-4|location=New York}}</ref>

The [[Hamburg cell]] in Germany included Islamists who eventually came to be key operatives in the 9/11 attacks.<ref>{{cite news |date=August 19, 2005 |title=The Hamburg connection |publisher=BBC News |url=http://news.bbc.co.uk/2/hi/europe/2349195.stm |access-date=June 26, 2011 |archive-date=May 30, 2013 |archive-url=https://web.archive.org/web/20130530031910/http://news.bbc.co.uk/2/hi/europe/2349195.stm |url-status=live }}</ref> [[Mohamed Atta]]; [[Marwan al-Shehhi]]; [[Ziad Jarrah]]; Ramzi bin al-Shibh; and [[Said Bahaji]] were all members of Al-Qaeda's Hamburg cell.<ref>"[http://www.9-11commission.gov/report/911Report_Ch5.htm 5 Al Qaeda Aims at the American Homeland]". [[9/11 Commission]]. {{webarchive|url=https://web.archive.org/web/20090816215318/http://www.9-11commission.gov/report/911Report_Ch5.htm|date=August 16, 2009}}.</ref> Bin Laden asserted that all Muslims must wage a defensive war against the United States and combat American aggression. He further argued that military strikes against American assets would send a message to the [[American people]], attempting to force the U.S. to re-evaluate its [[Israel–United States military relations|support to Israel]], and other aggressive policies.<ref>{{cite news |last1=Miller |first1=John |title="Greetings, America. My name is Osama Bin Laden..." |publisher=PBS |website=Frontline |url=https://www.pbs.org/wgbh/pages/frontline/shows/binladen/who/miller.html |archive-url=https://web.archive.org/web/20231124171126/https://www.pbs.org/wgbh/pages/frontline/shows/binladen/who/miller.html#:~:text=%22The%20American%20imposes%20himself%20on,the%20future%20of%20these%20children. |archive-date=November 24, 2023 |access-date=December 7, 2023 |url-status=live }}</ref> In a 1998 interview with American journalist [[John Miller (police official)|John Miller]], bin Laden stated:

{{Blockquote|text=We do not differentiate between those dressed in military uniforms and civilians; they are all targets in this fatwa. American history does not distinguish between civilians and military, not even women and children. They are the ones who used bombs against Nagasaki. Can these bombs distinguish between infants and military? America does not have a religion that will prevent it from destroying all people. So we tell the Americans as people and we tell the mothers of soldiers and American mothers in general that if they value their lives and the lives of their children, to find a nationalistic government that will look after their interests and not the [[International Jewish conspiracy|interests of the Jews]]. The continuation of tyranny will bring the fight to America, as [[1993 World Trade Center bombing|[the 1993 World Trade Center bomber]]] [[Ramzi Yousef|Ramzi [Yousef]]]  yourself and others did. This is my message to the American people: to look for a serious government that looks out for their interests and does not attack others, their lands, or their honor. My word to American journalists is not to ask why we did that but to ask what their government has done that forced us to defend ourselves.|source=<ref>{{cite news| url=https://www.pbs.org/wgbh/pages/frontline/shows/binladen/who/miller.html#:~:text=%22The%20American%20imposes%20himself%20on,the%20future%20of%20these%20children | title="Greetings, America. My name is Osama Bin Laden..."  | first1= John |last1= Miller | archive-url=https://web.archive.org/web/20010211145335/https://www.pbs.org/wgbh/pages/frontline/shows/binladen/who/miller.html | archive-date= February 11, 2001 | work=PBS}}</ref>|character=[[Osama bin Laden]]|title=his interview with [[John Miller (police official)|John Miller]], May 1998|multiline=}}

=== Osama bin Laden ===
{{Main|Osama bin Laden}}
{{further|Militant career of Osama bin Laden}}
[[File:Osama bin Laden portrait.jpg|thumb|[[Osama bin Laden]] in 1997 or 1998]]

Bin Laden orchestrated the September 11 attacks. He initially denied involvement, but later recanted his denial.<ref name="CBC 2004-10-29">{{cite news |date=October 29, 2004 |title=Bin Laden claims responsibility for 9/11 |publisher=CBC News |url=https://www.cbc.ca/news/world/bin-laden-claims-responsibility-for-9-11-1.513654 |access-date=September 1, 2011 |quote=Al-Qaeda leader Osama bin Laden appeared in a new message aired on an Arabic TV station Friday night, for the first time claiming direct responsibility for the 2001 attacks against the United States. |archive-date=February 18, 2010 |archive-url=https://web.archive.org/web/20100218142044/http://www.cbc.ca/world/story/2004/10/29/binladen_message041029.html |url-status=live }}</ref><ref name="BBC6Jul2011">{{cite news |title=Pakistan inquiry orders Bin Laden family to remain |url=https://www.bbc.co.uk/news/world-south-asia-14041604 |publisher=BBC News |date=July 6, 2011 |access-date=September 3, 2011 |archive-date=November 30, 2019 |archive-url=https://web.archive.org/web/20191130003148/https://www.bbc.co.uk/news/world-south-asia-14041604 |url-status=live }}</ref><ref name="ajNov2004">{{cite news|archive-url=https://web.archive.org/web/20070613014620/http://english.aljazeera.net/English/archive/archive?ArchiveId=7403 |archive-date=June 13, 2007 |url=http://english.aljazeera.net/English/archive/archive?ArchiveId=7403 |title=Full transcript of bin Laden's speech |publisher=Al Jazeera |date=November 2, 2004 |access-date=September 3, 2011}}</ref> [[Al Jazeera Media Network|Al Jazeera]] broadcast a statement by him on September 16, 2001: "I stress that I have not carried out this act, which appears to have been carried out by individuals with their own motivation".<ref>{{cite news |title=Pakistan to Demand Taliban Give Up Bin Laden as Iran Seals Afghan Border |url=https://www.foxnews.com/story/pakistan-to-demand-taliban-give-up-bin-laden-as-iran-seals-afghan-border |publisher=Fox News |date=September 16, 2001 |access-date=September 3, 2011 |archive-url=https://web.archive.org/web/20100523082548/http://www.foxnews.com/story/0,2933,34440,00.html |archive-date=May 23, 2010 |url-status=live }}</ref> In November 2001, U.S. forces recovered a videotape in which bin Laden, talking to [[Khaled bin Ouda bin Mohammed al-Harbi|Khaled al-Harbi]], [[Videos and audio recordings of Osama bin Laden#December 13, 2001|admitted foreknowledge]] of the attacks.<ref>{{cite news|title=Bin Laden on tape: Attacks 'benefited Islam greatly' |publisher=[[CNN]] |date=December 14, 2001 |url=http://archives.cnn.com/2001/US/12/13/ret.bin.laden.videotape/ |archive-url=https://web.archive.org/web/20071227125232/http://archives.cnn.com/2001/US/12/13/ret.bin.laden.videotape/ |archive-date=December 27, 2007 |url-status=dead |access-date=November 24, 2013 |quote=Reveling in the details of the fatal attacks, bin Laden brags in Arabic that he knew about them beforehand and said the destruction went beyond his hopes. He says the attacks "benefited Islam greatly".}}</ref> On December 27, 2001, a second video of bin Laden was released in which he, stopping short of admitting responsibility for the attacks, said:<ref>{{cite news |date=December 27, 2001 |title=Transcript: Bin Laden video excerpts |publisher=BBC News |url=http://news.bbc.co.uk/2/hi/middle_east/1729882.stm |access-date=September 3, 2011 |archive-date=July 27, 2019 |archive-url=https://web.archive.org/web/20190727043659/http://news.bbc.co.uk/2/hi/middle_east/1729882.stm |url-status=live }}</ref>{{blockquote|It has become clear that the West in general and America in particular have an unspeakable hatred for Islam.{{spaces}}... It is the hatred of [[crusaders]]. Terrorism against America deserves to be praised because it was a response to injustice, aimed at forcing America to stop its support for Israel, which kills our people.{{spaces}}... We say that the end of the United States is imminent, whether Bin Laden or his followers are alive or dead, for the awakening of the Muslim [[ummah]] [nation] has occurred.{{spaces}}... It is important to hit the economy (of the United States), which is the base of its military power...If the economy is hit they will become reoccupied.|author=Osama bin Laden}}

Shortly before the [[2004 United States presidential election|2004 U.S. presidential election]], bin Laden used a [[2004 Osama bin Laden video|taped statement]] to publicly acknowledge Al-Qaeda's involvement in the attacks.<ref name="CBC 2004-10-29" /> He admitted his direct link to the attacks and said they were carried out because:

{{blockquote| The events that affected my soul in a direct way started in 1982 when America permitted the Israelis to invade Lebanon and the American Sixth Fleet helped them in that. This bombardment began and many were killed and injured and others were terrorised and displaced.

I couldn't forget those moving scenes, blood and severed limbs, women and children sprawled everywhere. Houses were destroyed along with their occupants, high rises demolished over their residents, rockets raining down on our home without mercy...As I looked at those demolished towers in Lebanon, it entered my mind that we should punish the oppressor in kind and that we should destroy towers in America so that they taste some of what we tasted and so that they be deterred from killing our women and children.

And that day, it was confirmed to me that oppression and the intentional killing of innocent women and children is a deliberate American policy. Destruction is freedom and democracy, while resistance is terrorism and intolerance.<ref>{{cite news |last=Bin Ladin |first=Osama |url=https://www.aljazeera.com/news/2004/11/1/full-transcript-of-bin-ladins-speech |title=Full transcript of bin Ladin's speech |agency=Al Jazeera |date=November 1, 2004 |access-date=June 3, 2023 |archive-date=November 1, 2020 |archive-url=https://web.archive.org/web/20201101175357/https://www.aljazeera.com/news/2004/11/1/full-transcript-of-bin-ladins-speech |url-status=live }}</ref>}} Bin Laden personally directed his followers to attack the [[World Trade Center (1973–2001)|World Trade Center]] and the Pentagon.<ref>{{cite news|access-date=February 2, 2019|title=Bin Laden Dead – Where Are Other 9/11 Planners?|url=https://abcnews.go.com/Blotter/osama-bin-laden-dead-911-perpetrators-now/story?id=13511484|date=May 2, 2011|publisher=[[ABC News (United States)|ABC News]]|quote=While initially denying responsibility for the 9/11 attacks, Bin Laden took responsibility for them in a 2004 taped statement, saying that he had personally directed the hijackers.|archive-date=May 4, 2011|archive-url=https://web.archive.org/web/20110504215745/https://abcnews.go.com/Blotter/osama-bin-laden-dead-911-perpetrators-now/story?id=13511484|url-status=live}}</ref><ref>{{cite news|access-date=February 2, 2019|date=October 29, 2004|title=Bin Laden claims responsibility for 9/11|publisher=[[CBC News]]|url=https://www.cbc.ca/news/world/bin-laden-claims-responsibility-for-9-11-1.513654|archive-date=February 18, 2010|archive-url=https://web.archive.org/web/20100218142044/http://www.cbc.ca/world/story/2004/10/29/binladen_message041029.html|url-status=live}}</ref> Another video obtained by Al Jazeera in September 2006 showed bin Laden with one of the attacks' chief planners, [[Ramzi bin al-Shibh]], as well as hijackers, [[Hamza al-Ghamdi]] and [[Wail al-Shehri]], amidst making preparations for the attacks.<ref>{{cite news|url=https://www.cbc.ca/news/world/bin-laden-9-11-planning-video-aired-1.618703 |title=Bin Laden 9/11 planning video aired |publisher=[[CBC News]] |date=September 7, 2006 |archive-url=https://web.archive.org/web/20071013183902/https://www.cbc.ca/news/world/bin-laden-9-11-planning-video-aired-1.618703 |archive-date=October 13, 2007 |access-date=September 3, 2011}}</ref>

=== Khalid Sheikh Mohammed and other Al-Qaeda members ===
{{Main|Khalid Sheikh Mohammed|}}[[File:Khalid Shaikh Mohammed after capture.jpg|thumb|[[Khalid Sheikh Mohammed]] after his 2003 capture in [[Rawalpindi]], Pakistan]]
Journalist [[Yosri Fouda]] of the Arabic television channel [[Al Jazeera Media Network|Al Jazeera]] reported that in April 2002 Al-Qaeda member [[Khalid Sheikh Mohammed]] admitted his involvement in the attacks, along with Ramzi bin al-Shibh.<ref>{{cite news|url=https://www.theguardian.com/international/story/0,3604,906911,00.html |archive-url=https://web.archive.org/web/20080123195032/http://www.guardian.co.uk/international/story/0%2C3604%2C906911%2C00.html |archive-date=January 23, 2008 |title=We left out nuclear targets, for now |work=[[The Guardian]] |date=March 4, 2003 |access-date=September 3, 2011 |quote=Yosri Fouda of the Arabic television channel al-Jazeera is the only journalist to have interviewed Khalid Sheikh Mohammed, the al-Qaeda military commander arrested at the weekend. |location=London |url-status=dead}}</ref><ref>{{cite news |url=https://www.telegraph.co.uk/news/3685099/Alleged-911-mastermind-wants-to-confess-to-plot.html |archive-url=https://ghostarchive.org/archive/20220110/https://www.telegraph.co.uk/news/3685099/Alleged-911-mastermind-wants-to-confess-to-plot.html |archive-date=January 10, 2022 |url-access=subscription |url-status=live|title=Alleged 9/11 mastermind wants to confess to plot |work=[[The Daily Telegraph]] |date=October 10, 2008 |access-date=September 3, 2011 |location=London|first1=Tom|last1=Leonard |first2=Alex|last2=Spillius}}{{cbignore}}</ref><ref name="aljazeera2007">{{cite news |date=March 15, 2007 |title=September 11 suspect 'confesses' |publisher=[[Al Jazeera English|Al Jazeera]] |url=http://www.aljazeera.com/news/americas/2007/03/200852512026300115.html |access-date=September 3, 2011 |archive-date=September 27, 2019 |archive-url=https://web.archive.org/web/20190927221043/https://www.aljazeera.com/news/americas/2007/03/200852512026300115.html |url-status=live }}</ref> The 2004 ''[[9/11 Commission Report]]'' determined that the animosity which Mohammed, the principal architect of the 9/11 attacks, felt towards the United States had stemmed from his "violent disagreement with U.S. foreign policy favoring Israel".<ref name="9/11 Commission Report 2004 p147">9/11 Commission Report (2004), p. 147.</ref> Mohammed was also an adviser and financier of the [[1993 World Trade Center bombing]] and the uncle of [[Ramzi Yousef]], the lead bomber in that attack.<ref>{{cite news|url=http://www.washingtontimes.com/news/2009/aug/26/white-house-power-grabs/|title=White House power grabs|date=August 26, 2009|work=[[The Washington Times]]|access-date=September 3, 2011|archive-date=December 5, 2019|archive-url=https://web.archive.org/web/20191205144643/https://www.washingtontimes.com/news/2009/aug/26/white-house-power-grabs/|url-status=live}}</ref><ref>{{cite news|url=http://www.businessweek.com/news/2011-04-04/khalid-sheikh-mohammed-terror-indictment-unsealed-dismissed.html|archive-url=https://web.archive.org/web/20110417023034/http://www.businessweek.com/news/2011-04-04/khalid-sheikh-mohammed-terror-indictment-unsealed-dismissed.html|archive-date=April 17, 2011|title=Khalid Sheikh Mohammed Terror Indictment Unsealed, Dismissed |last1=Van Voris |first1=Bob |last2=Hurtado |first2=Patricia|date=April 4, 2011|work=[[Bloomberg BusinessWeek]]|access-date=September 3, 2011}}</ref> In late 1994, Mohammed and Yousef moved on to plan a new terrorist attack called the [[Bojinka plot]] planned for January 1995. Despite a failure and [[Ramzi Yousef#Arrest, conviction and prison life|Yousef's capture]] by U.S. forces the following month, the Bojinka plot would influence the later 9/11 attacks.{{sfn|Wright|2006|p={{page needed|date=September 2023}}}}

In "Substitution for Testimony of Khalid Sheikh Mohammed" from the trial of [[Zacarias Moussaoui]], five people are identified as having been completely aware of the operation's details. They are bin Laden, Khalid Sheikh Mohammed, [[Ramzi bin al-Shibh]], [[Abu Turab al-Urduni]] and [[Mohammed Atef]].<ref>{{cite web |title=Substitution for Testimony of Khalid Sheikh Mohammed |page=24 |url=http://www.vaed.uscourts.gov/notablecases/moussaoui/exhibits/defense/941.pdf |year=2006 |publisher=[[United States District Court for the Eastern District of Virginia]] |access-date=September 3, 2011 |archive-date=October 26, 2019 |archive-url=https://web.archive.org/web/20191026151908/http://www.vaed.uscourts.gov/notablecases/moussaoui/exhibits/defense/941.pdf |url-status=dead }}</ref>

=== Motives ===
{{Main|Motives for the September 11 attacks}}
{{Further|Fatwa of Osama bin Laden}}
Osama bin Laden's declaration of a [[Religious war|holy war]] against the United States, and a [[Fatwas of Osama bin Laden|1998 ''fatwā'' signed by bin Laden]] and others that called for the killing of Americans,<ref name="PBS 2013-11-28" /><ref name="1996 text">{{cite web |title=[Text of] Bin Laden's [1996] Fatwa |url=https://www.pbs.org/newshour/updates/military-july-dec96-fatwa_1996/ |url-status=live |archive-url=https://web.archive.org/web/20140419014901/http://www.pbs.org/newshour/updates/military-july-dec96-fatwa_1996/ |archive-date=April 19, 2014 |access-date=June 14, 2014 |publisher=[[PBS NewsHour]] |ref=August 23, 1996}}</ref> are seen by investigators as evidence of his motivation.<ref>Gunarathna, pp. 61–62.</ref> In November 2001, Bin Laden defended the attacks as retaliatory strikes against American atrocities against Muslims across the world. He also maintained that the attacks were not directed against women and children, asserting that the targets of the strikes were symbols of America's "economic and military power".<ref>{{cite book |last=Bin Laden |first=Osama |title=Messages to the World: The Statements of Osama bin Laden |publisher=Verso |year=2005 |isbn=1-84467-045-7 |editor=Lawrence |editor-first=Bruce |location=London |pages=139, 140, 141 |chapter=Declaration of Jihad |quote=The targets of September 11 were not women and children. The main targets were the symbol of the United States: their economic and military power.}}</ref><ref>{{Cite news |date=November 10, 2001 |title='Muslims have the right to attack America' |work=The Guardian |url=https://www.theguardian.com/world/2001/nov/11/terrorism.afghanistan1 |archive-url=https://web.archive.org/web/20130825215127/https://www.theguardian.com/world/2001/nov/11/terrorism.afghanistan1 |archive-date=August 25, 2013}}</ref>

In bin Laden's November 2002 "''[[Letter to the American people]]''", he identified al-Qaeda's motives for the attacks:
* [[Israel–United States military relations|U.S. support of Israel]]<ref name="bin Laden" /><ref name="Israel sources">
*Mearsheimer (2007), p. 67.
*Kushner (2003), p. 389.
*Murdico (2003), p. 64.
*Kelley (2006), p. 207.
*Ibrahim (2007), p. 276.
*{{harvp|Berner|2007|p=80}}</ref>
* Bin Laden's strategy to support and globally expand the [[Al-Aqsa Intifada]]<ref>{{cite web |date=November 24, 2002 |title=Full text: bin Laden's 'letter to America' |url=https://www.theguardian.com/world/2002/nov/24/theobserver |url-status=live |archive-url=https://web.archive.org/web/20141008120001/http://www.theguardian.com/world/2002/nov/24/theobserver |archive-date=October 8, 2014 |access-date=January 7, 2019 |work=The Guardian |quote=The blood pouring out of Palestine must be equally revenged. You must know that the Palestinians do not cry alone; their women are not widowed alone; their sons are not orphaned alone... American people have chosen, consented to, and affirmed their support for the Israeli oppression of the Palestinians, the occupation and usurpation of their land, and its continuous killing, torture, punishment and expulsion of the Palestinians. The American people have the ability and choice to refuse the policies of their government and even to change them if they want. (b) The American people are the ones who pay the taxes that fund the planes that bomb us in Afghanistan, the tanks that strike and destroy our homes in Palestine, the armies that occupy our lands in the Arabian Gulf, and the fleets that ensure the blockade of Iraq.}}</ref><ref>{{Cite book |last=Riedel |first=Bruce |title=The Search for Al Qaeda |publisher=Brookings Institution Press |year=2008 |isbn=978-0-8157-0451-5 |location=Massachusetts Avenue, N.W., Washington, DC, US |pages=5, 6 |chapter=1: The Manhattan Raid |quote=The Palestinian intifada, the fierce uprising in the fall of 2000 on the West Bank and Gaza, was a particularly powerful motivating event for.. bin Laden... The intifada's power over bin Laden's thinking about the 9/11 raid is underscored by his repeated attempts to push KSM to advance the timing of the crashes. In September of 2000, he urged KSM to tell Atta to attack immediately to respond to the Sharon visit to the holy sites in Jerusalem; Atta told bin Laden he was not ready yet. When bin Laden learned that Sharon, who had become Israel's prime minister in March 2001, was going to visit the White House early that summer, he again pressed Atta to attack immediately. And again Atta demurred, arguing he needed more time to get the plan and the team ready to go.}}</ref><ref>{{Cite book |last=Holbrook |first=Donald |title=The Al-Qaeda Doctrine |publisher=Bloomsbury |year=2014 |isbn=978-1-62356-314-1 |location=New York, NY, US |pages=145}}</ref><ref>{{cite book |last1=J. Greenberg |first1=Karen |title=Al Qaeda Now |publisher=Cambridge University Press |year=2005 |isbn=978-0-521-85911-0 |location=New York, US |pages=192–206 |chapter=October 21, 2001 – Interview with Tayseer Alouni |quote=Last year's blessed intifada helped us to push more for the Palestinian issue. This push helps the other cause. Attacking America helps the cause of Palestine and vice versa. No conflict between the two; on the contrary, one serves the other.}}</ref>
* Attacks against Muslims by [[Unified Task Force|U.S.-led coalition]] in Somalia
* U.S. support of the government of [[Philippines]] against Muslims in the [[Moro conflict]]
* U.S. support for the [[Israeli occupation of Southern Lebanon]]
* U.S. support of Russian atrocities against Muslims in [[Chechnya]]
* Pro-American governments in the Middle East (who "act as your agents") being against Muslim interests
* U.S. support of Indian oppression against Muslims in Kashmir
* The [[Operation Southern Watch|presence of U.S. troops in Saudi Arabia]]<ref>*Plotz, David (2001) [http://www.slate.com/articles/news_and_politics/assessment/2001/09/what_does_osama_bin_laden_want.html What Does Osama Bin Laden Want?] {{Webarchive|url=https://web.archive.org/web/20161115012459/http://www.slate.com/articles/news_and_politics/assessment/2001/09/what_does_osama_bin_laden_want.html |date=November 15, 2016 }}, ''Slate''
*{{harvp|Bergen|2001|p=3}}
*{{cite news |last=Yusufzai |first=Rahimullah |title=Face to face with Osama |url=https://www.theguardian.com/g2/story/0,3604,558075,00.html |url-status=dead |archive-url=https://web.archive.org/web/20080119011449/http://www.guardian.co.uk/g2/story/0%2C3604%2C558075%2C00.html |work=The Guardian |location=London |date=September 26, 2001 |access-date=September 3, 2011 |archive-date=January 19, 2008 }}
*{{cite news |title=US pulls out of Saudi Arabia |url=http://news.bbc.co.uk/2/hi/middle_east/2984547.stm |publisher=BBC News |date=April 29, 2003 |access-date=September 3, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172742/http://news.bbc.co.uk/2/hi/middle_east/2984547.stm |url-status=live }}
*{{cite news |url=https://www.wsj.com/articles/SB1025558570331929960 |title=Saga of Dr. Zawahri Sheds Light on the Roots of al Qaeda Terror |work=[[The Wall Street Journal]] |date=July 2, 2002 |access-date=September 3, 2011 |url-access=subscription |archive-date=December 30, 2018 |archive-url=https://web.archive.org/web/20181230220026/https://www.wsj.com/articles/SB1025558570331929960 |url-status=live }}
*{{cite web |url=http://www.9-11commission.gov/archive/hearing10/9-11Commission_Hearing_2004-04-13.htm |title=Tenth Public Hearing, Testimony of Louis Freeh |publisher=9/11 Commission |date=April 13, 2004 |access-date=September 3, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172014/https://9-11commission.gov/archive/hearing10/9-11Commission_Hearing_2004-04-13.htm%20 |url-status=live }}
*{{cite web |title=Jihad Against Jews and Crusaders: World Islamic Front Statement |date=February 23, 1998 |url=https://fas.org/irp/world/para/docs/980223-fatwa.htm |publisher=[[Federation of American Scientists]] |access-date=September 3, 2011 |archive-date=April 21, 2010 |archive-url=https://web.archive.org/web/20100421110549/http://www.fas.org/irp/world/para/docs/980223-fatwa.htm |url-status=live }}</ref>
* The [[sanctions against Iraq]]<ref name="bin Laden">*{{cite news |url=http://www.aljazeera.com/archive/2004/11/200849163336457223.html |title=Full transcript of bin Ladin's speech |publisher=Al Jazeera |access-date=April 10, 2012 |url-status=dead |archive-url=https://web.archive.org/web/20160101093303/http://www.aljazeera.com/archive/2004/11/200849163336457223.html |archive-date=January 1, 2016 }}
*{{cite news |first=Osama |last=bin Laden |title=Full text: bin Laden's 'letter to America' |date=November 24, 2002 |url=https://www.theguardian.com/world/2002/nov/24/theobserver |work=[[The Observer]] |access-date=September 3, 2011 |location=London |archive-date=July 28, 2013 |archive-url=https://web.archive.org/web/20130728133223/http://www.guardian.co.uk/world/2002/nov/24/theobserver |url-status=live }}</ref>
*[[Environmental destruction]]<ref>{{cite news| url=https://www.theguardian.com/world/2002/nov/24/theobserver |work=The Guardian |location=London |title=Full text: bin Laden's 'letter to America' |date=November 24, 2002 |access-date=April 26, 2010| archive-url=https://web.archive.org/web/20100418164357/http://www.guardian.co.uk/world/2002/nov/24/theobserver| archive-date=April 18, 2010 |url-status=live}}</ref><ref>{{cite news|url=https://www.mirror.co.uk/news/topstories/2008/04/23/osama-bin-laden-s-aide-ayman-al-zawahiri-rants-on-global-warming-89520-20391770/|title=Osama bin Laden's aide Ayman al-Zawahiri rants on global warming – Mirror.co.uk<!-- Bot generated title -->|website=[[Daily Mirror]]|access-date=May 14, 2023|archive-date=May 11, 2008|archive-url=https://web.archive.org/web/20080511161707/http://www.mirror.co.uk/news/topstories/2008/04/23/osama-bin-laden-s-aide-ayman-al-zawahiri-rants-on-global-warming-89520-20391770/|url-status=dead}}</ref><ref>{{cite news |url=http://www.nydailynews.com/news/world/2010/01/29/2010-01-29_al_qaeda_leader_osama_bin_laden_blasts_us_in_tape_for_global_warming.html |work=New York Daily News |title=Al Qaeda leader Osama Bin Laden blasts U.S. in audiotape spewing hate for... global warming |first=Brian |last=Kates |date=January 30, 2010 |access-date=December 7, 2023 |archive-date=February 1, 2010 |archive-url=https://web.archive.org/web/20100201222703/http://www.nydailynews.com/news/world/2010/01/29/2010-01-29_al_qaeda_leader_osama_bin_laden_blasts_us_in_tape_for_global_warming.html |url-status=live }}</ref>

After the attacks, bin Laden and [[Ayman al-Zawahiri]] released additional [[Videos and audio recordings of Osama bin Laden|recordings]], some of which repeated the above reasons. Two relevant publications were bin Laden's 2002 "''Letter to the American people''"<ref name="BLLTA">{{cite news|url=https://www.theguardian.com/world/2002/nov/24/theobserver |title=Full transcript of bin Laden's 'Letter to America' |work=The Guardian |date=November 24, 2002|access-date=September 3, 2011 |location=London|archive-url=https://web.archive.org/web/20190426123409/https://www.theguardian.com/world/2002/nov/24/theobserver |archive-date=April 26, 2019 }}</ref> and a 2004 videotape by bin Laden.<ref name="Full Ladin">{{cite news|url=http://www.aljazeera.com/archive/2004/11/200849163336457223.html |title=Full transcript of bin Ladin's speech |access-date=April 10, 2012 |last=bin Laden |first=Osama |publisher=[[Al Jazeera English|Al Jazeera]] |quote=So I shall talk to you about the story behind those events and shall tell you truthfully about the moments in which the decision was taken, for you to consider |url-status=dead |archive-url=https://web.archive.org/web/20160101093303/http://www.aljazeera.com/archive/2004/11/200849163336457223.html |archive-date=January 1, 2016 }}</ref>
{{quote box|[...] those young men, for whom God has cleared the way, didn't set out to kill children, but rather attacked the biggest centre of military power in the world, [[the Pentagon]], which contains more than 64,000 workers, a military base which has a big concentration of army and intelligence ... 
As for the [[World Trade Center (1973–2001)|World Trade Center]], the ones who were attacked and who died in it were part of a financial power. It wasn't a children's school! Neither was it a residence. The consensus is that most of the people who were in the towers were men who backed the biggest financial force in the world, which spreads mischief throughout the world.
| source = —Osama Bin Laden's interview with [[Tayseer Allouni]], October 21, 2001<ref>{{cite book |title=Messages to the World: The Statements of Osama bin Laden |publisher=Verso |year=2005 |isbn=1-84467-045-7 |editor=Bruce Lawrence |location=London |page=119}}</ref>
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As an adherent of [[Islam]], bin Laden believed that [[kuffar|non-Muslims]] are forbidden from having a permanent presence in the [[Arabian Peninsula]].<ref>{{cite book |last=Bergen |first=Peter L. |author-link=Peter L. Bergen |title=Holy War, Inc.: Inside the Secret World of Osama Bin Laden |year=2005 |publisher=Simon and Schuster |location=New York |isbn=978-0-7432-3467-2|url=https://books.google.com/books?id=sRhZDrJb0zgC&pg=PP1|access-date=March 20, 2020}}</ref> In 1996, [[Fatwas of Osama bin Laden|bin Laden issued]] a ''fatwā'' calling for American troops to leave Saudi Arabia. One analysis of suicide terrorism suggested that without U.S. troops in Saudi Arabia, Al-Qaeda likely would not have been able to get people to commit to suicide missions.<ref>{{cite book |last=Pape |first=Robert A. |author-link=Robert Pape |title=Dying to Win: The Strategic Logic of Suicide Terrorism |year=2005 |publisher=Random House |location=New York |isbn=978-0-8129-7338-9|url=https://archive.org/details/dyingtowinstrate00pape|access-date=March 20, 2020}}</ref> In the 1998 ''fatwā'', Al-Qaeda identified the Iraq sanctions as a reason to kill Americans, condemning the "protracted blockade" among other actions that constitute a declaration of war against "Allah, his messenger, and Muslims".<ref name="1998 Al Qaeda fatwā">{{cite web |url=https://fas.org/irp/world/para/docs/980223-fatwa.htm |title=1998 Al Qaeda fatwā |publisher=[[Federation of American Scientists]] (FAS) |date=February 23, 1998 |access-date=September 3, 2011 |archive-date=April 21, 2010 |archive-url=https://web.archive.org/web/20100421110549/http://www.fas.org/irp/world/para/docs/980223-fatwa.htm |url-status=live }}</ref>

In 2004, bin Laden claimed that the idea of destroying the towers had first occurred to him in 1982 when he witnessed Israel's bombardment of high-rise apartment buildings during the [[1982 Lebanon War]].<ref>Summers and Swan (2011), [https://archive.org/details/eleventhdayfulls0000summ/page/211/mode/1up pp. 211], [https://archive.org/details/eleventhdayfulls0000summ/page/506/mode/1up 506n].</ref><ref>Lawrence (2005), p. 239.</ref> Some analysts, including political scientists [[John Mearsheimer]] and [[Stephen Walt]], also claimed that U.S. support of Israel was a motive for the attacks.<ref name="Israel sources" /><ref name="guardian-20010926">{{cite news |url=https://www.theguardian.com/world/2001/sep/26/afghanistan.terrorism3 |title=Face to face with Osama |work=The Guardian |date=September 26, 2001 |location=London |access-date=September 3, 2011 |first=Rahimullah |last=Yusufzai |archive-date=January 19, 2008 |archive-url=https://web.archive.org/web/20080119011449/http://www.guardian.co.uk/g2/story/0,3604,558075,00.html |url-status=live }}</ref> In 2004 and 2010, bin Laden again connected the September 11 attacks with U.S. support of Israel, although most of the letters expressed bin Laden's disdain for President Bush and bin Laden's hope to "destroy and bankrupt" the U.S.<ref>{{cite news|title=Full transcript of bin Ladin's speech|url=http://www.aljazeera.com/archive/2004/11/200849163336457223.html%20online%20here|publisher=Al Jazeera|access-date=August 24, 2016|date=November 4, 2004|archive-date=November 14, 2016|archive-url=https://web.archive.org/web/20161114080708/http://www.aljazeera.com/archive/2004/11/200849163336457223.html%20online%20here|url-status=dead}}</ref><ref>In his taped broadcast from January 2010, bin Laden said "Our attacks against you [the United States] will continue as long as U.S. support for Israel continues.{{spaces}}... The message sent to you with the attempt by the hero Nigerian [[Umar Farouk Abdulmutallab]] is a confirmation of our previous message conveyed by the heroes of September{{spaces}}11". Quoted from [http://www.haaretz.com/news/bin-laden-attacks-on-u-s-to-go-on-as-long-as-it-supports-israel-1.265770 "Bin Laden: Attacks on U.S. to go on as long as it supports Israel"] {{webarchive |url=https://web.archive.org/web/20161216081625/http://www.haaretz.com/news/bin-laden-attacks-on-u-s-to-go-on-as-long-as-it-supports-israel-1.265770 |date=December 16, 2016 }}, in Haaretz.com</ref>

Other motives have been suggested in addition to those stated by bin Laden and Al-Qaeda. Some authors suggested the "humiliation" that resulted from the Islamic world falling behind the Western world—this discrepancy was rendered especially visible by globalization<ref>Bernard Lewis, 2004. In [[Bernard Lewis]]'s 2004 book ''[[The Crisis of Islam: Holy War and Unholy Terror]]'', he argues that animosity toward the West is best understood with the decline of the once powerful [[Ottoman empire]], compounded by the import of western ideas{{snd}}[[Arab socialism]], [[Liberal movements within Islam|Arab liberalism]] and [[Secularism in the Middle East|Arab secularism]]</ref><ref>In "The spirit of terrorism", [[Jean Baudrillard]] described 9/11 as the first global event that "questions the very process of globalization". {{cite web |url=http://homes.chass.utoronto.ca/~ikalmar/illustex/baudriterror.htm |title=The spirit of terrorism |last=Baudrillard |access-date=June 26, 2011 |archive-date=May 28, 2010 |archive-url=https://web.archive.org/web/20100528231925/http://www.chass.utoronto.ca/~ikalmar/illustex/baudriterror.htm |url-status=live }}</ref> and a desire to provoke the U.S. into a broader war against the Islamic world in the hope of motivating more allies to support Al-Qaeda. Similarly, others have argued the 9/11 attacks were a strategic move to provoke America into a war that would incite a [[pan-Islamism|pan-Islamic]] revolution.<ref>In an essay entitled "Somebody Else's Civil War", [[Michael Scott Doran]] argues the attacks are best understood as part of a religious conflict within the Muslim world and that bin Laden's followers "consider themselves an island of true believers surrounded by a sea of iniquity". Hoping that U.S. retaliation would unite the faithful against the West, bin Laden sought to spark revolutions in Arab nations and elsewhere. Doran argues the [[Osama bin Laden videos]] attempt to provoke a visceral reaction in the Middle East and ensure that Muslim citizens would react as violently as possible to an increase in U.S. involvement in their region. ({{cite magazine|url=https://www.foreignaffairs.com/articles/united-states/2002-01-01/somebody-elses-civil-war|title=Somebody Else's Civil War|first=Michael Scott|last=Doran|issue=January/February 2002|magazine=[[Foreign Affairs]]|access-date=December 5, 2009|url-access=subscription|archive-date=April 23, 2015|archive-url=https://web.archive.org/web/20150423172939/http://www.foreignaffairs.com/articles/57618/michael-scott-doran/somebody-elses-civil-war|url-status=live}} Reprinted in {{cite book|last1=Hoge|first1=James F.|last2=Rose|first2=Gideon|title=Understanding the War on Terror |publisher=Norton |year=2005 |location=New York|isbn=978-0-87609-347-4|pages=72–75}})</ref><ref>In ''The Osama bin Laden I Know'', [[Peter Bergen]] argues the attacks were part of a plan to cause the United States to ''increase'' its military and cultural presence in the Middle East, thereby forcing Muslims to confront the idea of a non-Muslim government and to eventually establish conservative Islamic governments in the region.({{harvp|Bergen|2006|p=229}})</ref>

=== Planning ===
{{Main|Planning of the September 11 attacks}}
[[File:911 - FEMA - WTC impacts (graphic).svg|thumb|alt=Ground zero and surrounding area as seen from directly above depicting where the two planes impacted the towers|Map of the attacks on the [[World Trade Center (1973–2001)|World Trade Center]]]]
[[File:World Trade Center, NY - 2001-09-11 - Debris Impact Areas.svg|thumb|Diagram of the World Trade Center attacks]]
Documents seized during the [[Killing of Osama bin Laden|2011 operation that killed bin Laden]] included notes handwritten by bin Laden in September 2002 with the heading "The Birth of the Idea of September 11". He describes how he was inspired by the crash of [[EgyptAir Flight 990]] on October 31, 1999, which was deliberately crashed by co-pilot [[Gameel Al-Batouti]], killing over 200 passengers. "This is how the idea of 9/11 was conceived and developed in my head, and that is when we began the planning" bin Laden continued, adding that no one but [[Mohammed Atef|Abu Hafs]] and Abu al-Khair knew about it at the time. The ''[[9/11 Commission Report]]'' identified Khalid Sheikh Mohammed as the architect of 9/11, but he is not mentioned in bin Laden's notes.<ref>{{cite book |last=Lahoud |first=Nelly |url=https://books.google.com/books?id=eoppEAAAQBAJ&pg=PA16 |title=The Bin Laden Papers: How the Abbottabad Raid Revealed the Truth about al-Qaeda, Its Leader and His Family |year=2022 |publisher=Yale University Press |isbn=978-0-300-26063-2 |location=New Haven (CT) |pages=16–19, 307}}<br />{{cite web |date=September 2002 |title=The Birth of the Idea of September 11 |url=https://www.cia.gov/library/abbottabad-compound/8F/8F496071D25B831EFBFD5299FBC0DF62_msoB4938.jpg |url-status=live |archive-url=https://web.archive.org/web/20220415162318/https://www.cia.gov/library/abbottabad-compound/8F/8F496071D25B831EFBFD5299FBC0DF62_msoB4938.jpg |archive-date=April 15, 2022 |access-date=April 15, 2022 |publisher=Central Intelligence Agency |language=ar}}</ref>

The attacks were conceived by [[Khalid Sheikh Mohammed]], who first presented it to [[Osama bin Laden]] in 1996.<ref>{{cite news |title=Suspect 'reveals 9/11 planning' |url=http://news.bbc.co.uk/2/hi/south_asia/3128802.stm |publisher=BBC News |date=September 22, 2003 |access-date=September 3, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172402/http://news.bbc.co.uk/2/hi/south_asia/3128802.stm%20 |url-status=live }}</ref> At that time, bin Laden and Al-Qaeda were in a period of transition, having just relocated back to Afghanistan from [[Sudan]].<ref name="911-ch5">''9/11 Commission Report'' (2004), Chapter 5, pp. ??{{page needed|date=September 2020}}</ref> The [[1998 United States embassy bombings|1998 African embassy bombings]] and bin Laden's February 1998 ''fatwā'' marked a turning point of Al-Qaeda's terrorist operation,<ref>''9/11 Commission Report'' (2004), p. 67.</ref> as bin Laden became intent on attacking the United States.

In late 1998 or early 1999, bin Laden approved Mohammed to go forward with organizing the plot.<ref>''9/11 Commission Report'' (2004), p. 149.</ref> Atef provided operational support, including target selections and helping arrange travel for the hijackers.<ref name="911-ch5" /> Bin Laden overruled Mohammed, rejecting potential targets such as the [[U.S. Bank Tower (Los Angeles)|U.S. Bank Tower]] in Los Angeles for lack of time.<ref>{{cite news |last=Lichtblau |first=Eric |title=Bin Laden Chose 9/11 Targets, Al Qaeda Leader Says |url=https://www.nytimes.com/2003/03/20/us/threats-and-responses-the-plot-bin-laden-chose-9-11-targets-al-qaeda-leader-says.html |work=The New York Times |date=March 20, 2003 |access-date=September 3, 2011 |archive-date=August 30, 2019 |archive-url=https://web.archive.org/web/20190830215929/https://www.nytimes.com/2003/03/20/us/threats-and-responses-the-plot-bin-laden-chose-9-11-targets-al-qaeda-leader-says.html |url-status=live }}</ref>{{sfnp|Wright|2006|p=308}}

Bin Laden provided leadership and financial support and was involved in selecting participants.{{sfnp|Bergen|2006|p=283}} He initially selected [[Nawaf al-Hazmi]] and [[Khalid al-Mihdhar]], both experienced jihadists who had fought in [[Bosnian war|Bosnia]]. Hazmi and Mihdhar arrived in the United States in mid-January 2000. In early 2000, Hazmi and Mihdhar took flying lessons in San Diego, California. Both spoke little English, performed poorly in flying lessons, and eventually served as secondary "muscle" hijackers.{{sfnp|Wright|2006|pp=309–315}}<ref>McDermott (2005), pp. 191–192.</ref>

In late 1999, a group of men from [[Hamburg]], Germany, arrived in Afghanistan. The group included [[Mohamed Atta]], [[Marwan al-Shehhi]], [[Ziad Jarrah]], and Ramzi bin al-Shibh.<ref>{{cite news |last=Bernstein |first=Richard |title=On Path to the U.S. Skies, Plot Leader Met bin Laden |url=https://www.nytimes.com/2002/09/10/national/10PLOT.html |work=The New York Times |date=September 10, 2002 |access-date=September 3, 2011 |archive-date=May 12, 2011 |archive-url=https://web.archive.org/web/20110512010444/http://www.nytimes.com/2002/09/10/national/10PLOT.html |url-status=live }}</ref> Bin Laden selected these men because they were educated, could speak English, and had experience living in the West.{{sfnp|Wright|2006|pp=304–307}} New recruits were routinely screened for special skills and Al-Qaeda leaders consequently discovered that [[Hani Hanjour]] already had a commercial pilot's license.{{sfnp|Wright|2006|p=302}}

Hanjour arrived in San Diego on December 8, 2000, joining Hazmi.<ref name="9/11 commission staff statement No. 16">{{cite news|title=9/11 commission staff statement No. 16|date=June 16, 2004|url=http://www.9-11commission.gov/staff_statements/staff_statement_16.pdf|publisher=9/11 Commission|access-date=September 11, 2012|archive-date=March 20, 2020|archive-url=https://web.archive.org/web/20200320032738/https://9-11commission.gov/staff_statements/staff_statement_16.pdf|url-status=live}}</ref>{{Rp|6–7}} They soon left for Arizona, where Hanjour took refresher training.<ref name="9/11 commission staff statement No. 16" />{{rp|7}} Marwan al-Shehhi arrived at the end of May 2000, while Atta arrived on June 3, 2000, and Jarrah arrived on June 27, 2000.<ref name="9/11 commission staff statement No. 16" />{{rp|6}} Bin al-Shibh applied several times for a visa to the United States, but as a Yemeni, he was rejected out of concerns he would overstay his visa.<ref name="9/11 commission staff statement No. 16" />{{rp|4, 14}} Bin al-Shibh stayed in Hamburg, providing coordination between Atta and Mohammed.<ref name="9/11 commission staff statement No. 16" />{{rp|16}} The three [[Hamburg cell]] members all took pilot training in South Florida at [[Huffman Aviation]].<ref name="9/11 commission staff statement No. 16" />{{rp|6}}

In the spring of 2001, the secondary hijackers began arriving in the United States.<ref>{{cite web|url=http://www.9-11commission.gov/staff_statements/911_TerrTrav_Monograph.pdf|title=Staff Monograph on 9/11 and Terrorist Travel|publisher=9/11 Commission|year=2004|access-date=September 3, 2011|archive-date=December 25, 2018|archive-url=https://web.archive.org/web/20181225172706/https://9-11commission.gov/staff_statements/911_TerrTrav_Monograph.pdf%20|url-status=live}}</ref> In July 2001, Atta met with bin al-Shibh in [[Tarragona]], Catalonia, Spain, where they coordinated details of the plot, including final target selection. Bin al-Shibh passed along bin Laden's wish for the attacks to be carried out as soon as possible.<ref name="irujo">{{cite news|url=http://elpais.com/diario/2004/03/21/espana/1079823611_850215.html |title=Atta recibió en Tarragona joyas para que los miembros del 'comando' del 11-S se hiciesen pasar por ricos saudíes|trans-title=Atta received jewellery in Tarragona so that members of the 9/11 'commando' could pass themselves off as wealthy Saudis.|work=El País|date=March 21, 2004|last=Irujo|first=Jose María|access-date=April 10, 2012|language=es}}</ref> Some of the hijackers received passports from corrupt Saudi officials who were family members or used fraudulent passports to gain entry.<ref>{{cite web |title=Entry of the 9/11 Hijackers into the United States Staff Statement No. 1 |url=http://govinfo.library.unt.edu/911/staff_statements/staff_statement_1.pdf |publisher=National Commission on Terrorist Attacks Upon The United States |page=2 |access-date=February 7, 2017 |archive-date=April 14, 2020 |archive-url=https://web.archive.org/web/20200414204904/https://govinfo.library.unt.edu/911/staff_statements/staff_statement_1.pdf |url-status=live }}</ref>

There have been a few theories that 9/11 was selected by the hijackers as the date of the attack because it resembled [[9-1-1]], the [[Emergency telephone number|phone number used to report emergencies]] in the United States. However, [[Lawrence Wright]] wrote that the hijackers chose the date when [[John III Sobieski]], the [[King of Poland]] and [[Grand Duke of Lithuania]], began the [[Battle of Vienna|battle]] that turned back the [[Ottoman Empire]]'s Muslim armies that were attempting to capture [[Vienna]] in 1683. Vienna was the seat of the [[Holy Roman Empire]] and [[Habsburg monarchy]], both major powers in Europe at the time. For Osama bin Laden, this was a date when the West gained some dominance over Islam, and by attacking on this date, he hoped to make a step in Islam "winning" the war for worldwide power and influence.<ref>{{cite magazine |last=Hudson |first=John |title=How jihadists schedule terrorist attacks |url=https://foreignpolicy.com/2013/05/03/how-jihadists-schedule-terrorist-attacks/ |magazine=[[Foreign Policy]] |date=May 3, 2013 |access-date=February 9, 2020 |language=en-US |archive-date=April 4, 2020 |archive-url=https://web.archive.org/web/20200404042748/https://foreignpolicy.com/2013/05/03/how-jihadists-schedule-terrorist-attacks/ |url-status=live }}</ref>

=== Prior intelligence ===
{{Main|September 11 intelligence before the attacks}}
In late 1999, Al-Qaeda associate [[Walid bin Attash]] ("Khallad") contacted Mihdhar and told him to meet in [[Kuala Lumpur]], Malaysia; Hazmi and [[Abu Bara al Yemeni]] would also be in attendance. The [[NSA]] intercepted a telephone call mentioning the meeting, Mihdhar, and the name "Nawaf" (Hazmi); while the agency feared "Something nefarious might be afoot", it took no further action.

The CIA had already been alerted by Saudi intelligence about Mihdhar and Hazmi being Al-Qaeda members. A CIA team broke into Mihdhar's [[Dubai]] hotel room and discovered that Mihdhar had a U.S. visa. While [[Alec Station]] alerted intelligence agencies worldwide, it did not share this information with the FBI. The [[Malaysian Special Branch]] observed the January 5, 2000, meeting of the two Al-Qaeda members and informed the CIA that Mihdhar, Hazmi, and Khallad were flying to [[Bangkok]], but the CIA never notified other agencies of this, nor did it ask the [[State Department]] to put Mihdhar on its watchlist. An FBI liaison asked permission to inform the FBI of the meeting but was told: "This is not a matter for the FBI".{{sfnp|Wright|2006|pp=310–312}}

By late June, senior counter-terrorism official [[Richard A. Clarke|Richard Clarke]] and CIA director [[George Tenet]] were "convinced that a major series of attacks was about to come", although the CIA believed the attacks would likely occur in Saudi Arabia or Israel.{{sfnp|Clarke|2004|pp=235–236}} In early July, Clarke put domestic agencies on "full alert", telling them, "Something spectacular is going to happen here, and it's going to happen soon". He asked the FBI and the State Department to alert the embassies and police departments, and the [[United States Department of Defense|Defense Department]] to go to "Threat Condition Delta".{{sfnp|Wright|2006|p=344}}{{sfnp|Clarke|2004|pp=236–237}} Clarke later wrote: <blockquote>Somewhere in CIA there was information that two known al Qaeda terrorists had come into the United States. Somewhere in the FBI, there was information that strange things had been going on at flight schools in the United States.{{spaces}}[...] They had specific information about individual terrorists from which one could have deduced what was about to happen. None of that information got to me or the White House.{{sfnp|Clarke|2004|pp=242–243}}</blockquote>

{{quote box|[...] by July [2001], with word spreading of a coming attack, a schism emerged among the senior leadership of al Qaeda. Several senior members reportedly agreed with [[Mullah Omar]]. Those who reportedly sided with [[Osama bin Laden|bin Ladin]] included [[Muhammad Atef|Atef]], [[Sulaiman Abu Ghaith|Sulayman Abu Ghayth]], and [[Khalid Sheikh Mohammed|KSM]]. But those said to have opposed him were weighty figures in the organization-including [[Mahfouz Ould al-Walid|Abu Hafs the Mauritanian]], [[Saeed al-Masri|Sheikh Saeed al Masri]], and [[Saif al-Adel|Sayf al Adl]]. One senior al Qaeda operative claims to recall Bin Ladin arguing that attacks against the United States needed to be carried out immediately to support [[Second Intifada|insurgency in the Israeli-occupied territories]] and protest the presence of U.S. forces in Saudi Arabia.
| source = —''[[9/11 Commission Report]]'', p. 251<ref>{{Cite book |title=[[9/11 Commission Report]] |year=2004 |isbn=0-16-072304-3 |edition=Official Government |publisher=United States Government Publishing Office |location=Washington D.C, US|last1=Kean |first1=Thomas |last2=Hamilton |first2=Lee |page=251 }}</ref>
| align = right
| width = 25em
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On July 13, Tom Wilshire, a CIA agent assigned to the FBI's international terrorism division, emailed his superiors at the CIA's [[Counterterrorism Center]] (CTC) requesting permission to inform the FBI that Hazmi was in the country and that Mihdhar had a U.S. visa. The CIA never responded.{{sfnp|Wright|2006|p=340}}

The same day, Margarette Gillespie, an FBI analyst working in the CTC, was told to review material about the Malaysia meeting. She was not told of the participant's presence in the U.S. The CIA gave Gillespie surveillance photos of Mihdhar and Hazmi from the meeting to show to FBI counterterrorism but did not tell her their significance. The Intelink database informed her not to share intelligence material with criminal investigators. When shown the photos, the FBI refused more details on their significance, and they were not given Mihdhar's date of birth or passport number.{{sfnp|Wright|2006|pp=340–343}} In late August 2001, Gillespie told the [[Immigration and Naturalization Service|INS]], the State Department, the [[United States Customs Service|Customs Service]], and the FBI to put Hazmi and Mihdhar on their watchlists, but the FBI was prohibited from using criminal agents in searching for the duo, hindering their efforts.{{sfnp|Wright|2006|pp=352–353}}

Also in July, a [[Phoenix, Arizona|Phoenix]]-based FBI agent sent a message to FBI headquarters, Alec Station, and FBI agents in New York alerting them to "the possibility of a coordinated effort by Osama bin Laden to send students to the United States to attend civil aviation universities and colleges". The agent, Kenneth Williams, suggested the need to interview flight school managers and identify all Arab students seeking flight training.{{sfnp|Wright|2006|p=350}} In July, Jordan alerted the U.S. that Al-Qaeda was planning an attack on the U.S.; "months later", Jordan notified the U.S. that the attack's codename was "The Big Wedding" and that it involved aeroplanes.{{sfnp|Yitzhak|2016|p=218}}

On August 6, 2001, the CIA's Presidential Daily Brief, designated "For the President Only", was entitled ''[[Bin Ladin Determined To Strike in US]]''. The memo noted that FBI information "indicates patterns of suspicious activity in this country consistent with preparations for hijackings or other types of attacks".<ref>{{cite web|title=The Osama bin Laden File: National Security Archive Electronic Briefing Book No. 343|url=http://nsarchive.gwu.edu/NSAEBB/NSAEBB343/|publisher=The National Security Archive|access-date=March 14, 2016|archive-date=July 13, 2017|archive-url=https://web.archive.org/web/20170713182539/http://nsarchive.gwu.edu/NSAEBB/NSAEBB343/|url-status=live}}</ref>

In mid-August, one [[Minnesota]] flight school alerted the FBI about [[Zacarias Moussaoui]], who had asked "suspicious questions". The FBI found that Moussaoui was a radical who had travelled to Pakistan, and the INS arrested him for overstaying his French visa. Their request to search his laptop was denied by FBI headquarters due to the lack of [[probable cause]].{{sfnp|Wright|2006|pp=350–351}}

The failures in intelligence-sharing were attributed to 1995 [[United States Department of Justice|Justice Department]] policies limiting intelligence-sharing, combined with CIA and NSA reluctance to reveal "sensitive sources and methods" such as tapped phones.{{sfnp|Wright|2006|pp=342–343}} Testifying before the [[9/11 Commission]] in April 2004, then—[[United States Attorney General|Attorney General]] [[John Ashcroft]] recalled that the "single greatest structural cause for the September 11th problem was the wall that segregated or separated criminal investigators and intelligence agents".{{sfnp|Javorsek II|Rose|Marshall|Leitner|2015|p=742}} Clarke also wrote: "[T]here were... failures to get information to the right place at the right time".{{sfnp|Clarke|2004|p=238}}

== Attacks ==
{{For timeline|Timeline for the day of the September 11 attacks}}

Early on the morning of Tuesday, September 11, 2001, [[Hijackers in the September 11 attacks|nineteen hijackers]] took control of four commercial airliners (two [[Boeing 757]]s and two [[Boeing 767]]s).<ref name="911-ch1" /> Large planes with long flights were selected for hijacking because they would have more fuel.<ref name="Chap7" /><!-- Weren't early morning flights also chosen because they would have fewer passengers to overcome? --><!-- wasn't it late taking off, which allowed the passengers to hear of the others? -->
{| class="wikitable"
|+Key info about the four flights
! rowspan="2"|Operator
! rowspan="2"|Flight number
! rowspan="2"|Aircraft type
! rowspan="2"|Time of departure*
! rowspan="2"|Time of crash*
! rowspan="2"|Departed from
! rowspan="2"|En route to
! rowspan="2"|Crash site
! colspan="5"|Fatalities<br />{{Nobold|(There were no survivors from the flights)}}
|-
!Crew
!Passengers<sup>†</sup>
!Ground<sup>§</sup>
!Hijackers
!Total<sup>‡</sup>
|-
|[[American Airlines]]
|[[American Airlines Flight 11|11]]
|[[Boeing 767|Boeing 767-223ER]]
|style="text-align:right;"|7:59&nbsp;a.m.
|style="text-align:right;"|8:46&nbsp;a.m.
|[[Logan International Airport]]
|[[Los Angeles International Airport]]
|[[List of tenants in 1 World Trade Center (1971–2001)|North Tower]] of the [[World Trade Center (1973–2001)|World Trade Center]], floors 93 to 99
|style="text-align:right;"|11
|style="text-align:right;"|76
|style="text-align:right;" rowspan="2" |2,606
|style="text-align:right;"|5
|style="text-align:right;" rowspan="2" |2,763
|-
|[[United Airlines]]
|[[United Airlines Flight 175|175]]
|[[Boeing 767]]–222
|style="text-align:right;"|8:14&nbsp;a.m.
|style="text-align:right;"|9:03&nbsp;am{{efn|name=Time}}
|Logan International Airport
|Los Angeles International Airport
|[[List of tenants in 2 World Trade Center|South Tower]] of the World Trade Center, floors 77 to 85
|style="text-align:right;"|9
|style="text-align:right;"|51
|style="text-align:right;"|5
|-
|American Airlines
|[[American Airlines Flight 77|77]]
|[[Boeing 757]]–223
|style="text-align:right;"|8:20&nbsp;a.m.
|style="text-align:right;"|9:37&nbsp;a.m.
|[[Washington Dulles International Airport]]
|Los Angeles International Airport
|West wall of [[The Pentagon|Pentagon]]
|style="text-align:right;"|6
|style="text-align:right;"|53
|style="text-align:right;"|125
|style="text-align:right;"|5
|style="text-align:right;"|189
|-
|United Airlines
|[[United Airlines Flight 93|93]]
|[[Boeing 757]]–222
|style="text-align:right;"|8:42&nbsp;a.m.
|style="text-align:right;"|10:03&nbsp;a.m.
|[[Newark Liberty International Airport|Newark Int'l Airport]]
|[[San Francisco International Airport]]
|Field in [[Stonycreek Township, Somerset County, Pennsylvania|Stonycreek Township]] near [[Shanksville, Pennsylvania|Shanksville]]
|style="text-align:right;"|7
|style="text-align:right;"|33
|style="text-align:right;"|0
|style="text-align:right;"|4
|style="text-align:right;"|44
|-
! scope="row" style="text-align:right" colspan="8" |Totals
|style="text-align:right;"|33
|style="text-align:right;"|213
|style="text-align:right;"|2,731
|style="text-align:right;"|19
|style="text-align:right;"|2,996
|}
'''*''' [[Eastern Time Zone|Eastern Daylight Time]] (UTC−04:00)<br />'''<sup>†</sup>''' Excluding hijackers<br />'''<sup>§</sup>''' Including emergency workers<br />'''<sup>‡</sup>''' Including hijackers

=== Crashes ===
{{See also|Media documentation of the September 11 attacks}}
{{multiple image
| total_width       = 290
| image1            = The North Tower burning on September 11, 2001.jpg
| image2            = WTC 2 plane crash (Myers clip6).webm
| image3            = Pentagon Security Camera 1.ogv
| image4            = Crash site of United Airlines flight 93.jpg
| caption1          = The North Tower shortly after [[American Airlines Flight 11]] crashed. The first attack.
| caption2          = [[United Airlines Flight 175]] crashes into [[2 World Trade Center]]. The second attack.
| direction         = vertical
| caption3          = Security camera footage of [[American Airlines Flight 77]] crashing into [[the Pentagon]];<ref name="jw">{{cite AV media |url=https://www.youtube.com/watch?v=L75Gga92WO8 |title=Flight 77, Video 2 |publisher=Judicial Watch |access-date=April 4, 2012 |archive-url=https://ghostarchive.org/varchive/youtube/20211214/L75Gga92WO8 |archive-date=December 14, 2021 |url-status=live |via=YouTube}}{{cbignore}}</ref> the plane collides with the Pentagon approximately 86 seconds after the start of the recording. The third attack.
| width1            = 
| align             = right
| alt4              = A grassfield
| caption4          = The crash site of [[United Airlines Flight 93]], near [[Stonycreek Township, Somerset County, Pennsylvania|Stonycreek Township]]
}}

At 7:59&nbsp;am, [[American Airlines Flight 11]] took off from [[Logan International Airport]] in [[Boston]].<ref>{{cite news |url=http://www.boston.com/news/packages/underattack/news/planes_reconstruction.htm |title=Probe reconstructs horror, calculated attacks on planes |last=Johnson |first=Glen |date=November 23, 2001 |work=The Boston Globe|archive-url=https://web.archive.org/web/20121202072139/http://www.boston.com/news/packages/underattack/news/planes_reconstruction.htm |archive-date=December 2, 2012 }}</ref> Fifteen minutes into the flight, five hijackers armed with [[Utility knife|boxcutter]]s took over the plane, injuring at least three people (and possibly killing one)<ref>{{cite news |title=Excerpt: A travel day like any other until some passengers left their seats |url=http://seattletimes.nwsource.com/html/nationworld/2001986488_planes23.html |work=[[The Seattle Times]] |date=July 23, 2004 |access-date=May 23, 2008|archive-url=https://web.archive.org/web/20111119033249/http://seattletimes.nwsource.com/html/nationworld/2001986488_planes23.html |archive-date=November 19, 2011 }}</ref><ref>{{cite news |title=Inside the failed Air Force scramble to prevent the Sept. 11 attacks |url=http://www.msnbc.msn.com/id/5315883/ |publisher=[[MSNBC]] |date=June 28, 2004 |access-date=May 23, 2008|url-status=dead |archive-url=https://web.archive.org/web/20090918164352/http://www.msnbc.msn.com/id/5315883/ |archive-date=September 18, 2009 }}</ref><ref>{{cite news |last=Woolley |first=Scott |title=Video Prophet |url=https://www.forbes.com/home/technology/forbes/2007/0423/068.html |date=April 23, 2007 |work=Forbes |access-date=May 23, 2008|archive-url=https://web.archive.org/web/20081216103647/http://www.forbes.com/home/technology/forbes/2007/0423/068.html |archive-date=December 16, 2008 }}</ref> before forcing their way into the cockpit. The terrorists also displayed an apparent explosive and sprayed [[Tear gas|mace]] into the cabin, to frighten the hostages into submission and further hinder resistance.<ref>{{Cite news|author=Sheehy, Gail |url=http://www.observer.com/node/48805 |archive-url=https://web.archive.org/web/20071207153421/http://www.observer.com/node/48805 |url-status=dead |archive-date=December 7, 2007 |title='Stewardess ID'd Hijackers Early, Transcripts Show' burden |work=New York Observer |date=February 15, 2004 |access-date=September 30, 2010}}</ref> Back at Logan, [[United Airlines Flight 175]] took off at 8:14&nbsp;am.<ref name="We have some planes">{{cite web|url=https://govinfo.library.unt.edu/911/report/911Report_Ch1.htm|title=WE HAVE SOME PLANES|publisher=National Commission on Terrorist Attacks Upon the United States|access-date=December 7, 2023|archive-date=December 5, 2004|archive-url=https://web.archive.org/web/20041205190225/https://govinfo.library.unt.edu/911/report/911Report_Ch1.htm|url-status=live}}</ref> Hundreds of miles southwest at [[Dulles International Airport]], [[American Airlines Flight 77]] left the runway at 8:20&nbsp;am.<ref name="We have some planes" /> Flight 175's journey proceeded normally for 28 minutes until 8:42&nbsp;am, when a group of five hijacked the plane, murdering both pilots and stabbing several crew members before assuming control of the aircraft. These hijackers also used bomb threats to instil fear into the passengers and crew,{{sfn|9/11 Commission|2004a|pp=7–8}} also spraying chemical weapons to disable any opposition.<ref>{{cite news|url=https://www.abc.net.au/news/specials/september-11-remembered/2011-09-06/september-11-timeline/2862086|title=September 11: From take-off to tragic loss|date=September 5, 2011|access-date=November 29, 2022|publisher=Australian Broadcasting Corporation|archive-date=November 29, 2022|archive-url=https://web.archive.org/web/20221129075152/https://www.abc.net.au/news/specials/september-11-remembered/2011-09-06/september-11-timeline/2862086|url-status=live}}</ref> Concurrently, [[United Airlines Flight 93]] departed from [[Newark Liberty International Airport|Newark International Airport]] in [[New Jersey]];<ref name="We have some planes" /> originally scheduled to pull away from the gate at 8:00&nbsp;am, the plane was running 42 minutes late.

At 8:46&nbsp;am, Flight 11 was deliberately crashed into the north face of the World Trade Center's North Tower (1 WTC) between the 93rd and 99th floors.<ref>{{cite web |url=http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB196/doc01.pdf |title=Flight Path Study – American Airlines Flight 11 |publisher=National Transportation Safety Board |date=February 19, 2002 |access-date=June 27, 2011 |archive-date=February 14, 2007 |archive-url=https://web.archive.org/web/20070214030913/http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB196/doc01.pdf |url-status=live }}</ref> The initial presumption by many was that it was an accident.<ref>{{cite web|url=https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5335a3.htm|title=Preliminary Results from the World Trade Center Evacuation Study – New York City, 2003|access-date=November 30, 2022|archive-date=December 4, 2018|archive-url=https://web.archive.org/web/20181204032648/https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5335a3.htm|url-status=live}}</ref> At 8:51&nbsp;am, American Airlines Flight 77 was also taken over by five hijackers who forcibly entered the cockpit 31 minutes after takeoff.<ref>{{cite web |last=Gregor |first=Joseph A. |url=https://www.ntsb.gov/doclib/foia/9_11/ATC_Report_AA77.pdf |title=ATC Report American Airlines Flight 77 |publisher=National Transportation Safety Board |date=December 21, 2001 |access-date=September 25, 2011|archive-url=https://web.archive.org/web/20121029094317/https://www.ntsb.gov/doclib/foia/9_11/ATC_Report_AA77.pdf |archive-date=October 29, 2012 }}</ref> Although they were equipped with knives,<ref>{{Cite news|url=https://www.washingtonpost.com/archive/politics/2001/09/12/on-flight-77-our-plane-is-being-hijacked/85b3c4b3-876b-4bb5-b1f7-00cc8c37b75e/|title='On Flight 77: 'Our Plane Is Being Hijacked'|newspaper=[[The Washington Post]]|date=September 12, 2001|access-date=November 27, 2022|archive-date=January 11, 2016|archive-url=https://web.archive.org/web/20160111151019/https://www.washingtonpost.com/archive/politics/2001/09/12/on-flight-77-our-plane-is-being-hijacked/85b3c4b3-876b-4bb5-b1f7-00cc8c37b75e/|url-status=live}}</ref> there were no reports of anyone on board being stabbed, nor did the two people who made phone calls mention the use of mace or a bomb threat.
[[File:Explosion following the plane impact into the South Tower (WTC 2) - B6019~11.jpg|thumb|[[United Airlines Flight 175]] hitting the [[2 World Trade Center (1971–2001)|South Tower]]]]
Flight 175 was flown into the South Tower's southern facade (2{{spaces}}WTC) between the 77th and 85th floors<ref>{{cite web |url=http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB196/doc03.pdf |title=Flight Path Study – United Airlines Flight 175 |publisher=National Transportation Safety Board |date=February 19, 2002 |access-date=June 27, 2011 |archive-date=June 17, 2014 |archive-url=https://web.archive.org/web/20140617050241/http://www2.gwu.edu/~nsarchiv/NSAEBB/NSAEBB196/doc03.pdf |url-status=live }}</ref> at 9:03&nbsp;am,{{efn|name=Time}} demonstrating that the first crash was a deliberate act of terrorism.<ref>{{cite news|title=9:03 a.m.: The 9/11 moment when many grasped a new reality|url=https://www.mercurynews.com/2021/09/10/903-a-m-the-9-11-moment-when-many-grasped-a-new-reality/|website=[[The Mercury News]]|date=September 10, 2021|access-date=February 5, 2023|archive-date=November 30, 2022|archive-url=https://web.archive.org/web/20221130094708/https://www.mercurynews.com/2021/09/10/903-a-m-the-9-11-moment-when-many-grasped-a-new-reality/|url-status=live}}</ref><ref>{{cite news|title='By 9:05 a.m., it was clear America was under attack'|url=https://www.cnbc.com/2021/09/11/it-was-the-loudest-explosion-ive-ever-heard-a-9/11-survivor-on-her-harrowing-escape-from-the-pentagon.html|publisher=[[CNBC]]|date=September 11, 2021|access-date=February 5, 2023|archive-date=November 30, 2022|archive-url=https://web.archive.org/web/20221130094707/https://www.cnbc.com/2021/09/11/it-was-the-loudest-explosion-ive-ever-heard-a-9/11-survivor-on-her-harrowing-escape-from-the-pentagon.html|url-status=live}}</ref>

Four men aboard Flight 93 struck suddenly, killing at least one passenger, after having waited 46 minutes—a holdup that proved disastrous for the terrorists when combined with the delayed takeoff.<ref>{{cite news|url=https://www.nytimes.com/2006/04/26/arts/united-93-and-the-politics-of-heroism.html|title='United 93' and the politics of heroism|newspaper=The New York Times|date=April 26, 2006|last1=Longman|first1=Jere|access-date=December 7, 2023|archive-date=March 6, 2023|archive-url=https://web.archive.org/web/20230306235027/https://www.nytimes.com/2006/04/26/arts/united-93-and-the-politics-of-heroism.html|url-status=live}}</ref> They stormed the cockpit and seized control of the plane at 9:28&nbsp;am, turning the plane eastbound towards Washington, D.C.<ref>{{cite news |last=Stout |first=David |title=Recording From Flight 93 Played at Trial |url=https://www.nytimes.com/2006/04/12/us/12cnd-moussaoui.html?hp&ex=1144900800&en=f6fc83f83a632d06&ei=5094&partner=homepage |date=April 12, 2006 |work=The New York Times |access-date=August 24, 2008 |archive-date=September 4, 2015 |archive-url=https://web.archive.org/web/20150904030034/http://www.nytimes.com/2006/04/12/us/12cnd-moussaoui.html?hp&ex=1144900800&en=f6fc83f83a632d06&ei=5094&partner=homepage |url-status=live }}</ref> Much like their counterparts on the first two flights, the fourth team used bomb threats and filled the cabin with mace.<ref>{{cite news |title=Transcript: Paula Zahn Now |date=April 12, 2006 |publisher=CNN|url=http://edition.cnn.com/TRANSCRIPTS/0604/12/pzn.01.html |access-date=April 5, 2010 |archive-date=October 21, 2012 |archive-url=https://web.archive.org/web/20121021015137/http://edition.cnn.com/TRANSCRIPTS/0604/12/pzn.01.html |url-status=live }}</ref>

Nine minutes after Flight 93's hijacking, Flight 77 crashed into the west side of the Pentagon.<ref>{{cite web |url=http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB196/doc02.pdf |title=Flight Path Study – American Airlines Flight 77 |publisher=National Transportation Safety Board |date=February 19, 2002 |access-date=June 27, 2011 |archive-date=August 24, 2006 |archive-url=https://web.archive.org/web/20060824050511/http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB196/doc02.pdf |url-status=live }}</ref> Because of the two delays,<ref>{{Cite news|url=https://www.washingtonpost.com/outlook/2021/09/09/flight-93-target-capitol/|title=What was Flight 93's target on 9/11?|newspaper=[[The Washington Post]]|date=September 9, 2021|access-date=November 27, 2022|archive-date=January 10, 2023|archive-url=https://web.archive.org/web/20230110042815/https://www.washingtonpost.com/outlook/2021/09/09/flight-93-target-capitol/|url-status=live}}</ref> the passengers and crew of Flight 93 had time to learn of the previous attacks through phone calls to the ground, and as a result an uprising was hastily organized to take control of the aircraft at 9:57&nbsp;am.<ref name="WP93">{{cite news |first=David |last=Snyder |title=Families Hear Flight 93's Final Moments |url=http://www.highbeam.com/doc/1P2-351703.html|archive-url=https://web.archive.org/web/20130602123513/http://www.highbeam.com/doc/1P2-351703.html|url-status=dead|archive-date=June 2, 2013|newspaper=The Washington Post |date=April 19, 2002 |access-date=November 12, 2013}}</ref> Within minutes, passengers had fought their way to the front of the cabin and began breaking down the cockpit door. Fearing their captives would gain the upper hand, the hijackers rolled the plane and pitched it into a nosedive,<ref name="Flight93Xscript">{{cite wikisource |title=Flight 93 Cockpit Transcript}}</ref><ref name="NPS Flight 93 Story">{{cite web |title=The Flight 93 Story |url=http://www.nps.gov/flni/historyculture/index.htm |publisher=National Park Service |access-date=September 21, 2011 |archive-date=January 12, 2015 |archive-url=https://web.archive.org/web/20150112214156/http://www.nps.gov/flni/historyculture/index.htm |url-status=live }}</ref> crashing into a field near Shanksville, Pennsylvania, southeast of Pittsburgh, at 10:03&nbsp;am. The plane was about twenty minutes away from reaching D.C. at the time of the crash, and its target is believed to have been either the [[United States Capitol|Capitol Building]] or the [[White House]].<ref name="Chap7">{{cite book |chapter=The Attack Looms |chapter-url=http://govinfo.library.unt.edu/911/report/911Report_Ch7.htm |year=2004 |title=''9/11 Commission Report'' |publisher=National Commission on Terrorist Attacks Upon the United States |access-date=September 1, 2011 |archive-date=December 5, 2012 |archive-url=https://archive.today/20121205050859/http://govinfo.library.unt.edu/911/report/911Report_Ch7.htm |url-status=live }}</ref><ref name="WP93" />

Some passengers and crew who called from the aircraft using the cabin air phone service and mobile phones provided details: several hijackers were aboard each plane; they used [[Mace (spray)|mace]], tear gas, or pepper spray to overcome attendants; and some people aboard had been stabbed.<ref name="93phone">
*{{cite news |last=McKinnon |first=Jim |title=The phone line from Flight 93 was still open when a GTE operator heard Todd Beamer say: 'Are you guys ready? Let's roll' |url=http://old.post-gazette.com/headlines/20010916phonecallnat3p3.asp |work=Pittsburgh Post-Gazette |date=September 16, 2001 |access-date=April 10, 2011 |archive-date=October 1, 2019 |archive-url=https://web.archive.org/web/20191001003507/http://old.post-gazette.com/headlines/20010916phonecallnat3p3.asp |url-status=dead }}
*{{cite news |title=Relatives wait for news as rescuers dig |url=http://europe.cnn.com/2001/US/09/12/family.reacts/index.html |publisher=CNN |date=September 13, 2001 |access-date=November 11, 2013 |archive-date=November 11, 2013 |archive-url=https://web.archive.org/web/20131111213433/http://europe.cnn.com/2001/US/09/12/family.reacts/index.html |url-status=live }}
*Summers and Swan (2011), pp. 58, 463n, 476n.
*{{cite news |last1=Wilgoren |first1=Jodi |author-link1=Jodi Rudoren |last2=Wong |first2=Edward |author-link2=Edward Wong |title=On Doomed Flight, Passengers Vowed To Perish Fighting |url=https://www.nytimes.com/2001/09/13/us/after-attacks-united-flight-93-doomed-flight-passengers-vowed-perish-fighting.html |url-status=live |work=The New York Times |date=September 13, 2001 |access-date=September 1, 2011 |archive-url=https://web.archive.org/web/20090820221831/https://www.nytimes.com/2001/09/13/us/after-attacks-united-flight-93-doomed-flight-passengers-vowed-perish-fighting.html |archive-date=August 20, 2009 }}
*{{cite news |last=Serrano |first=Richard A. |title=Moussaoui Jury Hears the Panic From 9/11 |url=https://www.latimes.com/archives/la-xpm-2006-apr-11-na-moussa11-story.html |work=[[Los Angeles Times]] |date=April 11, 2006 |access-date=September 1, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172359/http://articles.latimes.com/2006/apr/11/nation/na-moussa11 |url-status=live }}
*{{cite news |last1=Goo |first1=Sara Kehaulani |last2=Eggen |first2=Dan |title=Hijackers used Mace, knives to take over airplanes |url=http://www.sfgate.com/default/article/Hijackers-used-Mace-knives-to-take-over-2805009.php |work=San Francisco Chronicle |date=January 28, 2004 |access-date=November 12, 2013 |archive-date=November 12, 2013 |archive-url=https://web.archive.org/web/20131112202350/http://www.sfgate.com/default/article/Hijackers-used-Mace-knives-to-take-over-2805009.php |url-status=live }}
*{{cite news|last=Ahlers|first=Mike M.|url=http://www.cnn.com/2004/US/01/27/911.commis.knife/|title=9/11 panel: Hijackers may have had utility knives|date=January 27, 2004|access-date=September 1, 2011|publisher=CBS News|archive-date=June 4, 2010|archive-url=https://web.archive.org/web/20100604231807/http://www.cnn.com/2004/US/01/27/911.commis.knife/|url-status=live}}</ref> Reports indicated hijackers stabbed and killed pilots, flight attendants, and one or more passengers.<ref name="911-ch1">''The 9/11 Commission Report'', pp. 4–14.</ref><ref>{{cite news |url=http://transcripts.cnn.com/TRANSCRIPTS/0201/06/lklw.00.html |title=Encore Presentation: Barbara Olson Remembered |work=Larry King Live |publisher=CNN |date=January 6, 2002 |access-date=September 1, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172447/http://transcripts.cnn.com/TRANSCRIPTS/0201/06/lklw.00.html%20 |url-status=live }}</ref> According to the 9/11 Commission's final report, the hijackers had recently purchased multi-function hand tools and assorted [[Leatherman]]-type utility knives with locking blades (which were not forbidden to passengers at the time), but these were not found among the possessions left behind by the hijackers.<ref name="commission">{{cite web |title=National Commission Upon Terrorist Attacks in the United States |url=http://www.9-11commission.gov/archive/hearing7/9-11Commission_Hearing_2004-01-27.htm |publisher=National Commission Upon Terrorist Attacks in the United States |access-date=January 24, 2008 |date=January 27, 2004 |archive-date=September 5, 2011 |archive-url=https://web.archive.org/web/20110905073043/http://www.9-11commission.gov/archive/hearing7/9-11Commission_Hearing_2004-01-27.htm |url-status=live }}</ref><ref>Summers and Swan (2011), p. 343.</ref> A flight attendant on Flight 11, a passenger on Flight 175, and passengers on Flight 93 said the hijackers had bombs, but one of the passengers said he thought the bombs were fake. The FBI found no traces of explosives at the crash sites, and the 9/11 Commission concluded that the bombs were probably fake.<ref name="911-ch1" /> On at least two of the hijacked flights—American 11 and United 93—the terrorists claimed over the PA system that they were taking hostages and were returning to the airport to have a ransom demand met, a clear attempt to prevent passengers from fighting back. Both attempts failed, however, as both hijacker pilots in these instances (Mohamed Atta<ref>{{cite web|url=http://www.ntsb.gov/about/Documents/Flight_Path_Study_AA11.pdf|title=Flight Path Study – American Airlines Flight 11|publisher=[[National Transportation Safety Board]]|access-date=November 29, 2022|archive-date=November 5, 2015|archive-url=https://web.archive.org/web/20151105103018/http://www.ntsb.gov/about/Documents/Flight_Path_Study_AA11.pdf|url-status=live}}</ref> and Ziad Jarrah,<ref>{{cite news|last=Hirschkorn|first=Phil|title=On tape, passengers heard trying to retake cockpit|url=http://www.cnn.com/2006/LAW/04/12/moussaoui.trial/|date=April 12, 2006|publisher=CNN|access-date=November 29, 2022|archive-date=May 1, 2019|archive-url=https://web.archive.org/web/20190501233708/http://www.cnn.com/2006/LAW/04/12/moussaoui.trial/|url-status=live}}</ref> respectively) mistakenly transmitted their messages to ATC instead of the people on the plane as intended, tipping off the flight controllers that the planes had been hijacked.

[[Collapse of the World Trade Center|Three buildings in the World Trade Center collapsed]] due to fire-induced structural failure. Although the South Tower was struck 17 minutes after the North Tower, the plane's impact zone was far lower, at a much faster speed, and into a corner, with the unevenly-balanced additional structural weight causing it to collapse first at 9:59&nbsp;am,<ref>{{cite journal|last=National Institute of Standards and Technology|title=Final Reports from the NIST World Trade Center Disaster Investigation|journal=NIST|year=2005|url=https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf|access-date=December 7, 2023|archive-date=September 11, 2021|archive-url=https://web.archive.org/web/20210911011051/https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf|url-status=live}}</ref>{{rp|80}}<ref name="finalreport">{{cite web |work =9/11 Final Report of the National Commission|title=Collapse of WTC2|year=2004|url=https://9-11commission.gov/report/911Report.pdf|access-date=December 7, 2023|archive-date=September 12, 2017|archive-url=https://web.archive.org/web/20170912055527/https://9-11commission.gov/report/911Report.pdf|url-status=live}}</ref>{{rp|322}} having burned for 56 minutes{{efn|NIST and the 9/11 Commission both state that the collapse began at 9:58:59&nbsp;am, which is rounded to 9:59<ref>{{cite journal|last=National Institute of Standards and Technology|title=Final Reports from the NIST World Trade Center Disaster Investigation|journal=NIST|year=2005|url=https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf|access-date=December 7, 2023|archive-date=September 11, 2021|archive-url=https://web.archive.org/web/20210911011051/https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf|url-status=live}}</ref>{{rp|84}}<ref name="finalreport" />{{rp|322}} for simplicity. If the commission's claim that the South Tower was struck at 9:03:11 is to be believed, then the collapse began 55 minutes and 48 seconds after the crash, not 56 minutes.}} in the fire caused by the crash of United Airlines Flight 175 and the explosion of its fuel. The North Tower lasted another 29 minutes before collapsing at 10:28&nbsp;am,{{efn|The exact time of the North Tower's collapse initiation is disputed, with NIST dubbing the moment it began to collapse as being 10:28:22&nbsp;am.<ref>{{cite web |title=Final Report on the Collapse of World Trade Center Building 7 |url=https://www.govinfo.gov/content/pkg/GOVPUB-C13-4d4c17460292ee57ef313f6491fa8d1e/pdf/GOVPUB-C13-4d4c17460292ee57ef313f6491fa8d1e.pdf |publisher=National Institute of Standards and Technology |access-date=March 17, 2023 |archive-date=March 9, 2023 |archive-url=https://web.archive.org/web/20230309172011/https://www.govinfo.gov/content/pkg/GOVPUB-C13-4d4c17460292ee57ef313f6491fa8d1e/pdf/GOVPUB-C13-4d4c17460292ee57ef313f6491fa8d1e.pdf |url-status=live }}</ref> and the 9/11 Commission recording the time as 10:28:25.<ref name="DOD Cronk Biden Announces" />{{rp|329}}}} one hour and forty-two minutes{{efn|name=Time1}} after being struck by American Airlines Flight 11. When the North Tower collapsed, debris fell on the nearby [[7 World Trade Center (1987–2001)|7&nbsp;World Trade Center]] building (7{{spaces}}WTC), damaging the building and starting fires. These fires burned for nearly seven hours, compromising the building's structural integrity, and 7{{spaces}}WTC collapsed at 5:21{{spaces}}pm.<ref>''World Trade Center Building Performance Study'', Ch. 5 WTC 7{{snd}}section 5.5.4</ref>{{sfnp|''Final Report on the Collapse of World Trade Center Building 7''|2008|p=xxxvii}} The west side of the Pentagon sustained significant damage.

At 9:42&nbsp;am, the [[Federal Aviation Administration]] (FAA) grounded all civilian aircraft within the continental U.S., and civilian aircraft already in flight were told to land immediately.<ref>{{cite news |title=Chapter 1: "We have some planes" |url=http://govinfo.library.unt.edu/911/report/911Report_Ch1.pdf |work=The 9/11 Commission Report |date=July 22, 2004 |access-date=July 5, 2015 |archive-date=September 16, 2019 |archive-url=https://web.archive.org/web/20190916171709/http://govinfo.library.unt.edu/911/report/911Report_Ch1.pdf |url-status=live }}</ref> All international civilian aircraft were either turned back or redirected to airports in Canada or Mexico, and were banned from landing on [[United States territory]] for three days.<ref>{{cite web |title=Profiles of 9/11 – About 9/11|url=http://www.biography.com/profiles-of-9-11/about911.jsp |archive-url=https://web.archive.org/web/20110722151526/http://www.biography.com/profiles-of-9-11/about911.jsp |archive-date=July 22, 2011 |publisher=[[The Biography Channel]] |access-date=September 2, 2011}}</ref> The attacks created widespread confusion among news organizations and air traffic controllers. Among unconfirmed and often contradictory news reports aired throughout the day, one of the most prevalent claimed a car bomb had been detonated at the U.S. State Department's headquarters in Washington, D.C.<ref name="errors2">{{cite web |last=Miller |first=Mark |title=Three hours that shook America: A chronology of chaos |url=http://www.broadcastingcable.com/news/news-articles/three-hours-shook-america-chronology-chaos/93600 |date=August 26, 2002 |website=[[Broadcasting & Cable]] |access-date=September 2, 2011 |archive-date=January 30, 2014 |archive-url=https://web.archive.org/web/20140130020702/http://www.broadcastingcable.com/news/news-articles/three-hours-shook-america-chronology-chaos/93600 |url-status=live }}</ref> Another jet ([[Delta Air Lines Flight 1989]]) was suspected of having been hijacked, but the aircraft responded to controllers and landed safely in Cleveland, Ohio.<ref>{{cite news |last1=Adams |first1=Marilyn |last2=Levin |first2=Alan |last3=Morrison |first3=Blake |title=Part II: No one was sure if hijackers were on board |url=https://www.usatoday.com/news/sept11/2002-08-12-hijacker-daytwo_x.htm |work=[[USA Today]] |date=August 13, 2002 |access-date=September 2, 2011}}</ref>

In an April 2002 interview, [[Khalid Sheikh Mohammed]] and [[Ramzi bin al-Shibh]], who are believed to have organized the attacks, said Flight 93's intended target was the United States Capitol, not the White House.{{sfnp|Fouda|Fielding|2004|pp=158–159}} During the planning stage of the attacks, [[Mohamed Atta]] (Flight 11's hijacker and pilot) thought the White House might be too tough a target and sought an assessment from [[Hani Hanjour]] (who hijacked and piloted Flight 77).<ref name="The Eleventh Day pp 323">Summers and Swan (2011), p. 323.</ref> Mohammed said Al-Qaeda initially planned to target nuclear installations rather than the World Trade Center and the Pentagon, but decided against it, fearing things could "get out of control".<ref name="AlQaedaplotted2002">{{cite news |title=Al-Qaeda 'plotted nuclear attacks' |url=http://news.bbc.co.uk/2/hi/middle_east/2244146.stm |publisher=BBC News |date=September 8, 2002 |access-date=September 2, 2011 |archive-date=January 3, 2019 |archive-url=https://web.archive.org/web/20190103031125/http://news.bbc.co.uk/2/hi/middle_east/2244146.stm |url-status=live }}</ref> Final decisions on targets, according to Mohammed, were left in the hands of the pilots.<ref name="The Eleventh Day pp 323" /> If any pilot could not reach his intended target, he was to crash the plane.<ref name="Chap7" />

=== Casualties ===
{{Main|Casualties of the September 11 attacks|Lists of victims of the September 11 attacks}}
[[File:WONDER-R1-E008 (cropped).jpg|thumb|One of three observable falls from the South Tower.<ref>{{cite journal |publisher=[[National Institute of Standards and Technology]] |title=Final Reports from the NIST World Trade Center Disaster Investigation |journal=NIST |year=2005 |url=https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf |page=86 |access-date=November 21, 2022 |archive-date=September 11, 2021 |archive-url=https://web.archive.org/web/20210911011051/https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf |url-status=live }}</ref> A similar photograph of a victim from the North Tower titled ''[[The Falling Man]]'' gained wide acclamation.]]
The attack on the World Trade Center's North Tower alone{{efn|The [[Camp Speicher massacre|massacre at Camp Speicher]]―often described as the second deadliest act of terrorism in history after 9/11―is said to have killed between 1,095 and 1,700 people.<ref>{{cite web|title=1095 soldiers still missing since the Speicher massacre by ISIS|url=http://arabic.cnn.com/middleeast/2014/09/18/iraq-isis-camp-speicher|website=CNN Arabic|date=September 18, 2014|access-date=May 15, 2023|language=ar|archive-date=September 20, 2014|archive-url=https://web.archive.org/web/20140920011251/http://arabic.cnn.com/middleeast/2014/09/18/iraq-isis-camp-speicher|url-status=live}}</ref> The upper estimate would tie it with the attack on the World Trade Center's North Tower, but until the true death toll of the massacre becomes known, then the hijacking and crash of Flight 11 was the deadliest act of terrorism on record.}} made 9/11 the deadliest act of terrorism in history.<ref name="ourworldindata-terrorism-2996">{{Cite journal |last1=Ritchie |first1=Hannah |author1-link=Hannah Ritchie |last2=Hasell |first2=Joe |last3=Mathieu |first3=Edouard |last4=Appel |first4=Cameron |last5=Roser |first5=Max |author10-link=Max Roser |date=July 28, 2013 |title=Terrorism |url=https://ourworldindata.org/terrorism |url-status=live |archive-url=https://web.archive.org/web/20160424230128/http://ourworldindata.org/terrorism/ |archive-date=April 24, 2016 |access-date=July 12, 2023 |journal=[[Our World in Data]] |quote=Airline hijackings: 2,996 people died as a result of the 9/11 attacks, making it the most fatal terrorist incident in recorded history.}}</ref> Taken together, the four crashes killed 2,996 people (including the hijackers) and injured thousands more.<ref name='CBC-Winnipegger'>{{cite news |title=Winnipegger heads to NY for 9/11 memorial |date=September 9, 2011 |url=http://www.cbc.ca/news/canada/manitoba/winnipegger-heads-to-ny-for-9-11-memorial-1.991431 |publisher=CBC News |access-date=November 13, 2013 |quote=A total of 2,996 people died: 19 hijackers and 2,977 victims. |archive-date=November 13, 2013 |archive-url=https://web.archive.org/web/20131113021016/http://www.cbc.ca/news/canada/manitoba/winnipegger-heads-to-ny-for-9-11-memorial-1.991431 |url-status=live }}</ref> The death toll included 265 on the four planes (from which there were no survivors); 2,606 in the World Trade Center and the surrounding area; and 125 at the Pentagon.<ref name="edition.cnn.com">{{cite news |title=Accused 9/11 plotter Khalid Sheikh Mohammed faces New York trial |url=http://edition.cnn.com/2009/CRIME/11/13/khalid.sheikh.mohammed/index.html |publisher=CNN |date=November 13, 2009 |access-date=September 2, 2011 |archive-date=October 28, 2014 |archive-url=https://web.archive.org/web/20141028165022/http://edition.cnn.com/2009/CRIME/11/13/khalid.sheikh.mohammed/index.html |url-status=live }}</ref><ref>{{cite news |url=http://www.cnn.com/2006/US/05/16/pentagon.video/index.html |title=First video of Pentagon 9/11 attack released |publisher=CNN|date=May 16, 2006 |access-date=September 2, 2011 |archive-url=https://web.archive.org/web/20060923103317/http://www.cnn.com/2006/US/05/16/pentagon.video/index.html |archive-date=September 23, 2006|url-status=live}}</ref> Most who died were civilians, as well as 343 firefighters, 72 law enforcement officers, 55 military personnel, and the 19 terrorists.<ref>{{cite news |last=Stone |first=Andrea |url=https://www.usatoday.com/news/sept11/2002-08-20-pentagon_x.htm |title=Military's aid and comfort ease 9/11 survivors' burden |work=USA Today |date=August 20, 2002 |access-date=September 2, 2011 |archive-date=June 27, 2012 |archive-url=https://web.archive.org/web/20120627082049/http://www.usatoday.com/news/sept11/2002-08-20-pentagon_x.htm |url-status=live }}</ref><ref>{{cite web|url=http://www.orgsites.com/va/asis151/Sep11Memorial.pdf |title=September 11, 2001 Memorial |work=New York State Intelligence Center |archive-url=https://web.archive.org/web/20160326025722/http://www.orgsites.com/va/asis151/Sep11Memorial.pdf |archive-date=March 26, 2016 |url-status=dead}}</ref> More than 90 countries lost citizens in the attacks.<ref name="countries_deaths">{{cite web|title=A list of the countries whose citizens died as a result of the attacks on September 11, 2001 |publisher=[[Bureau of International Information Programs|U.S. Department of State, Office of International Information Programs]] |url=http://usinfo.state.gov/is/img/assets/4756/9_11onepager1.pdf |access-date=March 18, 2016 |url-status=dead |archive-url=https://web.archive.org/web/20080411152231/http://usinfo.state.gov/is/img/assets/4756/9_11onepager1.pdf |archive-date=April 11, 2008}}</ref>

In New York City, more than 90% of those who died in the towers had been at or above the points of impact. In the North Tower, between 1,344<ref>{{cite news|date=September 10, 2003|title=Two Years Later: The 91st Floor; The Line Between Life and Death, Still Indelible|work=The New York Times|url=https://www.nytimes.com/2003/09/10/us/two-years-later-the-91st-floor-the-line-between-life-and-death-still-indelible.html|access-date=December 5, 2022|archive-date=December 5, 2022|archive-url=https://web.archive.org/web/20221205201711/https://www.nytimes.com/2003/09/10/us/two-years-later-the-91st-floor-the-line-between-life-and-death-still-indelible.html|url-status=live}}</ref> and 1,402<ref>{{cite news|website=[[Forbes]]|title=9/11 Survivors And Thrivers|access-date=December 5, 2022|last=Bousquette|first=Isabelle|url=https://www.forbes.com/sites/isabellebousquette/2021/09/10/911-survivors-and-thrivers/?sh=285a95f2552d|archive-date=December 5, 2022|archive-url=https://web.archive.org/web/20221205201710/https://www.forbes.com/sites/isabellebousquette/2021/09/10/911-survivors-and-thrivers/?sh=285a95f2552d|url-status=live}}</ref> people were at, above or one floor below the point of impact and all died. Hundreds were killed instantly when the plane struck.<ref>{{cite web |url=http://www.9-11commission.gov/report/911Report_Ch9.htm |title=Heroism and Horror |year=2004 |publisher=National Commission on Terrorist Attacks upon the United States |access-date=July 1, 2006 |archive-date=August 15, 2007 |archive-url=https://web.archive.org/web/20070815141749/http://www.9-11commission.gov/report/911Report_Ch9.htm |url-status=live }}</ref> The estimated 800 people<ref name="102Mins">{{cite news |last=Dwyer |first=Jim |author2=Lipton, Eric |title=102 Minutes: Last Words at the Trade Center; Fighting to Live as the Towers Die |url=https://www.nytimes.com/2002/05/26/nyregion/102-minutes-last-words-at-the-trade-center-fighting-to-live-as-the-towers-die.html |date=May 26, 2002 |work=The New York Times |access-date=December 5, 2022|archive-url=https://web.archive.org/web/20131114063928/http://www.nytimes.com/2002/05/26/nyregion/102-minutes-last-words-at-the-trade-center-fighting-to-live-as-the-towers-die.html |archive-date=November 14, 2013 |url-status=live }}</ref> who survived the impact were trapped and died in the fires or from smoke inhalation; fell or jumped from the tower to escape the smoke and flames; or were killed in the building's collapse. The destruction of all three staircases in the North Tower when Flight 11 hit made it impossible for anyone from the impact zone upward to escape. 107 people not trapped by the impact died.<ref name="NISTcasualties">{{harvp|Sunder|2005|p=48}}</ref> When Flight 11 struck between floors 93 and 99, the 92nd floor was rendered inescapable: the crash severed all elevator shafts while falling debris blocked the stairwells, ensuring the deaths of all 69 workers on the floor.

In the South Tower, around 600 people were on or above the 77th floor when Flight 175 struck; few survived. As with the North Tower, hundreds were killed at the moment of impact. Unlike those in the North Tower, the estimated 300 survivors<ref name="102Mins" /> of the crash were not technically trapped, but most were either unaware that a means of escape still existed or were unable to use it. One stairway, [[Stairwell A]], narrowly avoided being destroyed, allowing 14 people located on the floors of impact (including [[Stanley Praimnath]], a man who saw the plane coming at him) and four more from the floors above to escape. New York City [[9-1-1]] operators who received calls from people inside the tower were not well informed of the situation as it rapidly unfolded and as a result, told callers not to descend the tower on their own.<ref>{{cite book |last=National Commission on Terrorist Attacks |title=''The 9/11 Commission Report'' |publisher=W. W. Norton & Company |date=July 22, 2004 |url=https://archive.org/details/911commissionrep00nati/page/294 |page=[https://archive.org/details/911commissionrep00nati/page/294 294] |isbn=978-0-393-32671-0 |access-date=January 24, 2014 |edition=first }}</ref> In total, 630 people died in the South Tower, fewer than half the number killed in the North Tower.<ref name="NISTcasualties" /> Of the 100–200 people witnessed jumping or falling to their deaths,<ref>{{cite news |url=http://usatoday30.usatoday.com/news/sept11/2002-09-02-jumper_x.htm|title=Desperation forced a horrific decision|work=USA Today|access-date=April 18, 2015|archive-date=September 6, 2019|archive-url=https://web.archive.org/web/20190906201041/https://usatoday30.usatoday.com/news/sept11/2002-09-02-jumper_x.htm|url-status=live}}</ref> only three recorded sightings were from the South Tower.<ref>{{cite journal|last=National Institute of Standards and Technology|title=Final Reports from the NIST World Trade Center Disaster Investigation|journal=NIST|year=2005|url=https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf|access-date=December 7, 2023|archive-date=September 11, 2021|archive-url=https://web.archive.org/web/20210911011051/https://nvlpubs.nist.gov/nistpubs/Legacy/NCSTAR/ncstar1-5av1.pdf|url-status=live}}</ref>{{rp|86}} Casualties in the South Tower were significantly reduced because some occupants decided to leave the building immediately following the first crash, and because Eric Eisenberg, an executive at [[Aon (company)|AON Insurance]], decided to evacuate the floors occupied by AON (92 and 98–105) following the impact of Flight 11. The 17-minute gap allowed over 900 of the 1,100 AON employees present to evacuate from above the 77th floor before the South Tower was struck; Eisenberg was among the nearly 200 who did not escape. Similar pre-impact evacuations were carried out by [[Fiduciary Trust Company International|Fiduciary Trust]], [[Corporation Service Company|CSC]], and Euro Brokers, all of whom had offices on floors above the point of impact. The failure to order a full evacuation of the South Tower after the first plane crash into the North Tower was described by ''[[USA Today]]'' as "one of the day's great tragedies".<ref name="Purpura 2007 p300">{{cite book |last=Purpura |first=Philip |title=Security and Loss Prevention: An Introduction |chapter-url=https://books.google.com/books?id=ir4gbdZLlOEC&pg=PA300|access-date=September 16, 2017 |edition=5th |year=2007 |publisher=Elsevier |isbn=978-0-08-055400-6 |page=300 |chapter=Life safety, fire protection, and emergencies |quote=Almost all the 600 people in the top floors of the south tower died after a second hijacked airliner crashed in the 80th floor shortly after 9{{spaces}}am The failure to evacuate the building was one of the day's great tragedies.}}</ref>

As exemplified in the photograph ''[[The Falling Man]]'', more than 200 people fell to their deaths from the burning towers, most of whom were forced to [[Jumper (suicide)|jump]] to escape the extreme heat, fire and smoke.<ref name="horrificdecision">{{cite news |url=https://www.usatoday.com/news/sept11/2002-09-02-jumper_x.htm |title=Desperation forced a horrific decision |work=USA Today |date=September 2, 2002 |last1=Cauchon |first1=Dennis |last2=Moore |first2=Martha |access-date=September 2, 2011 |archive-date=September 1, 2012 |archive-url=https://web.archive.org/web/20120901152537/http://www.usatoday.com/news/sept11/2002-09-02-jumper_x.htm |url-status=live }}</ref> Some occupants of each tower above the point of impact made their way toward the roof in the hope of helicopter rescue, but the roof access doors were locked.<ref>{{cite news|last1=Paltrow|first1=Scot|title=Could Helicopters Have Saved People From the Top of the Trade Center?|url=https://www.wsj.com/articles/SB1003784754436648720|website=The Wall Street Journal|date=October 23, 2001|access-date=January 22, 2017|archive-date=August 13, 2021|archive-url=https://web.archive.org/web/20210813051841/https://www.wsj.com/articles/SB1003784754436648720|url-status=live}}</ref> No plan existed for helicopter rescues, and the combination of roof equipment, thick smoke and intense heat prevented helicopters from approaching.<ref>{{cite news|url=https://www.cbsnews.com/news/poor-info-hindered-9-11-rescue/|title=Poor Info Hindered 9/11 Rescue|publisher=CBS News|date=May 18, 2004|access-date=September 2, 2011|archive-date=December 25, 2018|archive-url=https://web.archive.org/web/20181225172234/https://www.cbsnews.com/news/poor-info-hindered-9-11-rescue/|url-status=live}}</ref>

At the World Trade Center complex, 414 emergency workers died as they tried to rescue people and fight fires, while another law enforcement officer was killed when United 93 crashed. The [[New York City Fire Department]] (FDNY) lost 343 firefighters, including a chaplain and two [[paramedics]].<ref>{{Cite web|url=https://nyfd.com/9_11_wtc.html|title=The Unofficial Home Page of FDNY|publisher=New York City Fire Department|access-date=December 7, 2023|archive-date=April 8, 2023|archive-url=https://web.archive.org/web/20230408020920/https://nyfd.com/9_11_wtc.html|url-status=live}}</ref><ref>{{cite web |title=Deadliest incidents resulting in the deaths of 8 or more firefighters |url=https://www.nfpa.org/News-and-Research/Data-research-and-tools/Emergency-Responders/Firefighter-fatalities-in-the-United-States/Deadliest-incidents-resulting-in-the-deaths-of-8-or-more-firefighters |publisher=[[National Fire Protection Association]] |access-date=December 7, 2023 |archive-date=March 28, 2019 |archive-url=https://web.archive.org/web/20190328084413/https://www.nfpa.org/News-and-Research/Data-research-and-tools/Emergency-Responders/Firefighter-fatalities-in-the-United-States/Deadliest-incidents-resulting-in-the-deaths-of-8-or-more-firefighters |url-status=live }}</ref><ref>{{cite web |date=June 11, 2002 |title=Congressional Record, Vol. 148, No. 76 |url=https://www.congress.gov/107/crec/2002/06/11/CREC-2002-06-11.pdf |publisher=Government Printing Office |page=H3312 |quote=[[Joel Hefley|Mr. Hefley]]: That fateful Tuesday we lost 72 police officers, the largest single loss of law enforcement personnel in a single day in the history of our country. |access-date=December 7, 2023 |archive-date=March 24, 2022 |archive-url=https://web.archive.org/web/20220324004649/https://www.congress.gov/107/crec/2002/06/11/CREC-2002-06-11.pdf |url-status=live }}</ref> The [[New York City Police Department]] (NYPD) lost 23 officers.<ref>{{cite news |title=Post-9/11 report recommends police, fire response changes |url=https://www.usatoday.com/news/nation/2002-08-19-nypd-nyfd-report_x.htm |date=August 19, 2002 |agency=Associated Press |work=USA Today |access-date=September 2, 2011 |archive-date=August 20, 2011 |archive-url=https://web.archive.org/web/20110820043759/http://www.usatoday.com/news/nation/2002-08-19-nypd-nyfd-report_x.htm |url-status=live }}</ref> The [[Port Authority Police Department]] (PAPD) lost 37 officers.<ref>{{cite news|title=Police back on day-to-day beat after 9/11 nightmare|url=http://edition.cnn.com/2002/US/07/20/wtc.police/|date=July 21, 2002|publisher=CNN|access-date=November 12, 2013|archive-date=November 13, 2013|archive-url=https://web.archive.org/web/20131113015111/http://edition.cnn.com/2002/US/07/20/wtc.police/|url-status=live}}</ref> Eight emergency medical technicians and paramedics from private emergency medical services units were killed.<ref>{{cite web|url=http://www.world-memorial.org/Tribute/EMS/medics.html|title=EMT & Paramedics|access-date=August 18, 2015|archive-url=https://web.archive.org/web/20170203041213/http://www.world-memorial.org/Tribute/EMS/medics.html|archive-date=February 3, 2017|url-status=dead}}</ref> Almost all of the emergency personnel who died at the scene were killed as a result of the towers collapsing, with the exception of one who was struck by a civilian falling from the South Tower.<ref>{{Cite news|url=https://www.cbc.ca/documentaries/the-passionate-eye/september-11-2001-5-firsthand-stories-from-people-who-survived-1.6130622|title=September 11, 2001: 5 firsthand stories from people who survived|date=September 11, 2021|publisher=[[Canadian Broadcasting Corporation]]|access-date=November 1, 2022|language=en|archive-date=March 6, 2023|archive-url=https://web.archive.org/web/20230306234907/https://www.cbc.ca/documentaries/the-passionate-eye/september-11-2001-5-firsthand-stories-from-people-who-survived-1.6130622|url-status=live}}</ref>

[[Cantor Fitzgerald]] L.P. (an investment bank on the North Tower's 101st–105th floors) lost 658 employees, considerably more than any other employer.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/americas/5282060.stm?lsf |title=Cantor rebuilds after 9/11 losses |publisher=BBC News |date=September 4, 2006 |access-date=September 2, 2011 |archive-date=April 6, 2008 |archive-url=https://web.archive.org/web/20080406160843/http://news.bbc.co.uk/2/hi/americas/5282060.stm?lsf |url-status=live }}</ref> [[Marsh & McLennan Companies|Marsh Inc.]], located immediately below Cantor Fitzgerald on floors 93–100, lost 358 employees,<ref>{{cite web|url=http://memorial.mmc.com/|title=Marsh & McLennan Companies 9/11 Memorial|access-date=September 7, 2011|archive-date=August 18, 2011|archive-url=https://web.archive.org/web/20110818143251/http://memorial.mmc.com/|url-status=live}}</ref><ref>{{cite web |url=http://www.mmc.com/about/history.php |title=Milestones of Marsh & McLennan Companies |access-date=September 7, 2011 |archive-date=April 26, 2014 |archive-url=https://web.archive.org/web/20140426233407/http://www.mmc.com/about/history.php |url-status=dead }}</ref> and 175 employees of [[Aon Corporation]] were killed.<ref>{{cite news |url=http://www.investmentnews.com/article/20070911/REG/70911011 |title=Industry honors fallen on 9/11 anniversary |publisher=InvestmentNews |last=Siegel |first=Aaron |date=September 11, 2007 |access-date=September 2, 2011 |archive-date=November 14, 2012 |archive-url=https://web.archive.org/web/20121114124815/http://www.investmentnews.com/article/20070911/REG/70911011 |url-status=live }}</ref> The [[National Institute of Standards and Technology]] (NIST) estimated that about 17,400 civilians were in the World Trade Center complex at the time of the attacks.{{sfnp|Averill|2005|loc="Occupant Behavior, Egress, and Emergency Communications"}}{{Reference page|location=xxxiii}} Turnstile counts from the Port Authority suggest 14,154 people were typically in the Twin Towers by 8:45{{spaces}}a.m.{{sfnp|Dwyer|Flynn|2005|p=266}} Most people below the impact zone safely evacuated.<ref>{{cite news |url=https://www.nytimes.com/2002/05/26/nyregion/102-minutes-last-words-at-the-trade-center-fighting-to-live-as-the-towers-die.html |title=Last Words at the Trade Center; Fighting to Live as the Towers Die |last1=Dwyer |first1=Jim |first2=Eric |last2=Lipton |first3=Kevin |last3=Flynn |first4=James |last4=Glanz |work=The New York Times |date=May 26, 2002 |access-date=September 2, 2011 |display-authors=etal |archive-date=September 12, 2009 |archive-url=https://web.archive.org/web/20090912025748/http://www.nytimes.com/2002/05/26/nyregion/102-minutes-last-words-at-the-trade-center-fighting-to-live-as-the-towers-die.html |url-status=live }}</ref>

In [[Arlington County, Virginia]], 125 Pentagon workers died when Flight 77 crashed into the building's western side. 70 were civilians and 55 were military personnel, many of whom worked for the [[United States Army]] or the [[United States Navy]]. The Army lost 47 civilian employees, six civilian contractors, and 22 soldiers, while the Navy lost six civilian employees, three civilian contractors, and 33 sailors. Seven [[Defense Intelligence Agency]] (DIA) civilian employees and one [[Office of the Secretary of Defense]] contractor died.<ref name="national">{{cite web|title=National Commission on Terrorist Attacks upon the United States|publisher=U.S. Congress|date=August 21, 2004|url=http://www.9-11commission.gov/report/index.htm|access-date=September 8, 2006|archive-date=September 3, 2011|archive-url=https://web.archive.org/web/20110903025127/http://www.9-11commission.gov/report/index.htm|url-status=live}}</ref>{{sfnp|Goldberg et al.|2007|pp=208–212}}<ref>{{cite web |title=September 11, 2001 Pentagon Victims |url=http://www.patriotresource.com/wtc/victims/pentagon.html |publisher=Patriot Resource |access-date=March 18, 2016 |archive-date=June 25, 2019 |archive-url=https://web.archive.org/web/20190625175936/http://www.patriotresource.com/wtc/victims/pentagon.html |url-status=live }}</ref> [[Timothy Maude]], a [[Lieutenant General]] and Army Deputy Chief of Staff, was the highest-ranking military official killed at the Pentagon.<ref name="arlington">{{cite web|title=Remembering the Lost: Timothy J. Maude, Lieutenant General, United States Army|publisher=Arlington National Cemetery|date=September 22, 2001|url=http://www.arlingtoncemetery.net/tjmaude.htm|access-date=April 16, 2001|archive-date=May 23, 2011|archive-url=https://web.archive.org/web/20110523142334/http://www.arlingtoncemetery.net/tjmaude.htm|url-status=live}}</ref>

Weeks after the attack, the death toll was estimated to be over 6,000, more than twice the number of deaths eventually confirmed.<ref>{{cite news |url=http://edition.cnn.com/2001/US/09/29/gen.america.under.attack/index.html |title=Source: Hijacking suspects linked to Afghanistan |publisher=CNN |date=September 30, 2001 |access-date=September 2, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225171616/http://edition.cnn.com/2001/US/09/29/gen.america.under.attack/index.html%20 |url-status=live }}</ref> The city was only able to identify remains for about 1,600 of the World Trade Center victims. The medical examiner's office collected "about 10,000 unidentified bone and tissue fragments that cannot be matched to the list of the dead".<ref name="CBS2">{{cite news |title=Ground Zero Forensic Work Ends |publisher=CBS News |date=February 23, 2005 |url=https://www.cbsnews.com/news/ground-zero-forensic-work-ends/ |access-date=September 2, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172509/https://www.cbsnews.com/news/ground-zero-forensic-work-ends/ |url-status=live }}</ref> Bone fragments were still being found in 2006 by workers who were preparing to demolish the damaged [[Deutsche Bank Building]].<ref>{{cite web |url=https://www.theguardian.com/world/2006/apr/15/september11.usa |title=Bone fragments from 9/11 found on skyscraper roof |publisher=The Guardian |date=April 14, 2006 |access-date=August 23, 2024}}</ref>

In 2010, a team of anthropologists and archaeologists searched for human remains and personal items at the [[Fresh Kills Landfill]], where 72 more human remains were recovered, bringing the total found to 1,845. DNA profiling continues in an attempt to identify additional victims.<ref>{{cite news |last=Andrade |first=Mariano |title=Scientists still struggle to identify 9/11 remains |url=http://news.discovery.com/human/psychology/world-trade-center-remains-110826.htm |agency=Agence France-Presse |date=August 25, 2011 |access-date=September 5, 2011 |work=[[Discovery News]] |archive-date=April 3, 2015 |archive-url=https://web.archive.org/web/20150403064003/http://news.discovery.com/human/psychology/world-trade-center-remains-110826.htm |url-status=live }}</ref><ref>{{cite news |url=http://www.nydailynews.com/new-york/remains-wtc-worker-ernest-james-40-id-ten-years-9-11-article-1.945620 |title=Remains of WTC worker Ernest James, 40, ID'd ten years after 9/11 |last=Lemre |first=Jonathan |work=New York Daily News |date=August 24, 2011 |access-date=April 10, 2012 |archive-date=September 12, 2012 |archive-url=https://web.archive.org/web/20120912163530/http://www.nydailynews.com/new-york/remains-wtc-worker-ernest-james-40-id-ten-years-9-11-article-1.945620 |url-status=live }}</ref><ref name="DNAContinue">{{cite news |first=Bobby |last=Cuza |title=9/11 A Decade Later: DNA Matching Efforts To Continue At WTC Site |date=June 11, 2011 |url=http://www.ny1.com/content/143516/9-11-a-decade-later--remains-from-wtc-tested-by-latest-dna-tech |archive-url=https://web.archive.org/web/20140920211012/http://www.ny1.com/content/143516/9-11-a-decade-later--remains-from-wtc-tested-by-latest-dna-tech |archive-date=September 20, 2014 |publisher=[[NY1]] |access-date=September 21, 2011}}</ref> In 2014, three coffin-size cases carrying 7,930 unidentified remains were transferred to a medical examiner's repository located at the same site as the [[National September 11 Memorial & Museum]].<ref>{{Cite news |last=Farrell |first=Stephen |date=May 10, 2014 |title=In 'Ceremonial Transfer,' Remains of 9/11 Victims Are Moved to Memorial |url=https://www.nytimes.com/2014/05/11/nyregion/remains-of-9-11-victims-are-transferred-to-trade-center-site.html |access-date=May 21, 2024 |work=The New York Times |language=en-US |issn=0362-4331}}</ref> Victims' families are permitted to visit a private "reflection room" which is closed to the public. The choice to place the remains in an underground area attached to a museum has been controversial; families of some victims have attempted to have the remains instead interred in a separate, above-ground monument.<ref>{{Cite news |last=Paolicelli |first=Alyssa |date=September 11, 2023 |title=Some families of unidentified 9/11 victims want remains moved above ground |url=https://ny1.com/nyc/manhattan/news/2023/09/08/some-families-of-unidentified-9-11-victims-want-remains-moved-above-ground |access-date=May 20, 2024 |work=NY1}}</ref>

In August 2017, the 1,641st victim was identified as a result of newly available DNA technology,<ref>{{cite news|url=https://www.bbc.co.uk/news/world-us-canada-40855907|title=9/11 victim identified 16 years on|date=August 7, 2017|publisher=BBC News|access-date=December 7, 2023|archive-date=November 29, 2022|archive-url=https://web.archive.org/web/20221129165713/https://www.bbc.co.uk/news/world-us-canada-40855907|url-status=live}}</ref> and a 1,642nd during July 2018.<ref name="no1642">{{cite news|url=https://www.cbsnews.com/amp/news/september-11-2001-attacks-remains-victim-scott-michael-johnson-identified/|title="Finality": 9/11 victim's remains identified 17 years later|date=July 26, 2018|publisher=[[CBS News]]|access-date=December 7, 2023|archive-date=March 24, 2023|archive-url=https://web.archive.org/web/20230324190315/https://www.cbsnews.com/amp/news/september-11-2001-attacks-remains-victim-scott-michael-johnson-identified/|url-status=live}}</ref> Three more victims were identified in October 2019,<ref>{{cite news |date=October 18, 2019 |title=New York 9/11 Victim Identified 18 Years After Attack |work=ABC WNEP-16 |url=https://www.wnep.com/article/news/new-york-9-11-victim-identified-18-years-after-attack/523-5d8a00b6-4e72-4d47-a5c1-a9d8f89ec82c |url-status=live |access-date=February 13, 2021 |archive-url=https://web.archive.org/web/20200808125056/https://www.wnep.com/article/news/new-york-9-11-victim-identified-18-years-after-attack/523-5d8a00b6-4e72-4d47-a5c1-a9d8f89ec82c |archive-date=August 8, 2020}}</ref> two in September 2021<ref name="2021-Sep">{{cite news |date=September 7, 2021 |title=2 new 9/11 victims identified through DNA testing, first new IDs since Oct. 2019 |url=https://www.audacy.com/wwjnewsradio/news/national/2-new-9-11-victims-identified-through-dna-testing-first-new-ids-since-oct-2019 |access-date=September 7, 2021 |archive-date=September 8, 2021 |archive-url=https://web.archive.org/web/20210908004755/https://www.audacy.com/wwjnewsradio/news/national/2-new-9-11-victims-identified-through-dna-testing-first-new-ids-since-oct-2019 |url-status=live }}</ref> and an additional two in September 2023.<ref name=":0">{{Cite web |last=Sottile |first=Kristina Sgueglia, Zoe |date=September 8, 2023 |title=Two new 9/11 victims identified, the first identifications in two years |url=https://www.cnn.com/2023/09/08/us/september-11-new-victim-identifications/index.html |access-date=September 10, 2023 |website=CNN |language=en |archive-date=October 24, 2023 |archive-url=https://web.archive.org/web/20231024141323/https://www.cnn.com/2023/09/08/us/september-11-new-victim-identifications/index.html |url-status=live }}</ref> As of September 2023, 1,104 victims remain unidentified,<ref name=":0"/> amounting to 40% of the deaths in the World Trade Center attacks.<ref name="2021-Sep"/> On September 25, 2023, the FDNY reported that the department had now lost the same number of members to 9/11-related illnesses as it did on the day of the attacks.<ref>{{cite web|url=https://www.cbsnews.com/newyork/news/fdny-loses-343rd-member-to-911-related-illness-as-many-as-died-on-day-of-attacks/|title=FDNY loses 343rd member to 9/11 related illness -- as many as died on day of attacks|publisher=[[CBS New York]]|language=en-US|url-status=live|date=September 25, 2023|access-date=September 25, 2023|archive-date=September 25, 2023|archive-url=https://archive.today/20230925140642/https://www.cbsnews.com/newyork/news/fdny-loses-343rd-member-to-911-related-illness-as-many-as-died-on-day-of-attacks/}}</ref><ref>{{cite web|url=https://abc7ny.com/fdny-death-toll-september-11-emt-911-related-illness/13824058/|title=FDNY lives lost from 9/11-related illnesses now matches death toll from the day|publisher=[[WABC-TV]]|language=en-US|url-status=live|date=September 25, 2023|access-date=September 25, 2023|archive-date=September 25, 2023|archive-url=https://archive.today/20230925140931/https://abc7ny.com/fdny-death-toll-september-11-emt-911-related-illness/13824058/}}</ref>

=== Damage ===
{{further|Collapse of the World Trade Center|List of buildings damaged or destroyed in the September 11 attacks}}
[[File:World Trade Center Site After 9-11 Attacks With Original Building Locations.jpg|thumb|The [[World Trade Center site]], called [[World Trade Center site|Ground Zero]], with an overlay showing the locations of the original buildings]]
The [[World Trade Center (1973–2001)|Twin Towers]], the [[Marriott World Trade Center|Marriott Hotel (3{{spaces}}WTC)]], 7{{spaces}}WTC, and [[St. Nicholas Greek Orthodox Church]] were destroyed.<ref name="wtcstudy">{{cite web|url=http://www.fema.gov/rebuild/mat/wtcstudy.shtm |title=World Trade Center Building Performance Study |date=May 2002 |publisher=[[Federal Emergency Management Agency]] |access-date=September 3, 2011 |archive-url=https://web.archive.org/web/20101016101226/http://www.fema.gov/rebuild/mat/wtcstudy.shtm |archive-date=October 16, 2010 |url-status=dead}}</ref> The U.S. Customs House ([[6 World Trade Center]]), [[4 World Trade Center (1975–2001)|4{{spaces}}World Trade Center]], [[5 World Trade Center]], and both pedestrian bridges connecting buildings were severely damaged. All surrounding streets were in ruins.<ref>{{Cite web |title=Route 9A Reconstruction |url=https://www.stantec.com/en/projects/united-states-projects/r/route-9-reconstruction |access-date=June 28, 2024 |website=stantec.com |language=en}}</ref> The last fires at the World Trade Center site were extinguished on December 20.<ref>{{cite news |url=https://www.theguardian.com/world/2001/dec/20/september11.usa |title=Ground Zero stops burning, after 100 days |website=The Guardian |date=December 20, 2001 |access-date=May 5, 2018 |archive-date=July 13, 2018 |archive-url=https://web.archive.org/web/20180713032752/https://www.theguardian.com/world/2001/dec/20/september11.usa |url-status=live }}</ref>

The [[Deutsche Bank Building]] was damaged and was later condemned as uninhabitable because of toxic conditions; it was deconstructed starting in 2007.<ref name="The Eleventh Day pp 75">Summers and Swan (2011), p. 75.</ref><ref name="130 Liberty Finally Gone from Ground Zero">{{cite news |first=Matt |last=Chaban |title=130 Liberty Finally Gone from Ground Zero |date=February 9, 2011 |url=http://www.commercialobserver.com/2011/02/130-liberty-finally-gone-from-ground-zero/ |work=[[The New York Observer]] |access-date=April 10, 2012 |archive-date=May 11, 2013 |archive-url=https://web.archive.org/web/20130511062921/http://commercialobserver.com/2011/02/130-liberty-finally-gone-from-ground-zero/ |url-status=live }}</ref><ref>''World Trade Center Building Performance Study{{snd}}Bankers Trust Building'', pp. {{page needed|date=September 2020}}</ref><ref>{{cite web|title=The Deutsche Bank Building at 130 Liberty Street|publisher=Lower Manhattan Construction Command Center|url=http://www.renewnyc.com/plan_des_dev/130Liberty/default.asp|access-date=September 2, 2011|archive-date=August 20, 2011|archive-url=https://web.archive.org/web/20110820043655/http://www.renewnyc.com/plan_des_dev/130Liberty/default.asp|url-status=live}}</ref> Buildings of the [[Brookfield Place (New York City)|World Financial Center]] were damaged.<ref name="The Eleventh Day pp 75" />  The [[Borough of Manhattan Community College]]'s Fiterman Hall was condemned due to extensive damage, and then reopened in 2012.<ref>{{cite news |last=Shapiro |first=Julie |title=Students Return to Rebuilt Fiterman Hall 11 Years After 9/11 |url=https://www.dnainfo.com/new-york/20120827/financial-district/students-return-rebuilt-fiterman-hall-11-years-after-911 |url-status=dead |website=DNAinfo New York |date=August 27, 2012 |access-date=October 27, 2017 |archive-url=https://web.archive.org/web/20171027125835/https://www.dnainfo.com/new-york/20120827/financial-district/students-return-rebuilt-fiterman-hall-11-years-after-911 |archive-date=October 27, 2017 }}</ref>

Other neighbouring buildings (including [[90 West Street]] and the [[Barclay–Vesey Building|Verizon Building]]) suffered major damage but have been restored.<ref name="nyconstruction">{{cite web |title=Verizon Building Restoration |url=http://newyork.construction.com/projects/TopProjects04/Verizon.asp |url-status=live |publisher=New York Construction (McGraw Hill) |access-date=September 2, 2011 |archive-url=https://web.archive.org/web/20110511183933/http://newyork.construction.com/projects/TopProjects04/Verizon.asp |archive-date=May 11, 2011}}</ref> [[Brookfield Place (New York City)|World Financial Center]] buildings, [[One Liberty Plaza]], the [[Millenium Hilton]], and 90 Church Street had moderate damage and have been restored.<ref>''World Trade Center Building Performance Study{{snd}}Peripheral Buildings'', pp. {{page needed|date=September 2020}}</ref> Communications equipment on top of the North Tower was also destroyed, with only [[WCBS-TV]] maintaining a backup transmitter on the [[Empire State Building]], but media stations were quickly able to reroute the signals and resume their broadcasts.<ref name="wtcstudy" /><ref>{{cite web |last=Bloomfield |first=Larry |url=http://sysdesignshowcase.broadcastengineering.com/ar/broadcasting_new_york_broadcasters |title=New York broadcasters rebuild |publisher=Broadcast Engineering |date=October 1, 2001 |access-date=September 3, 2011 |archive-url=https://web.archive.org/web/20080604040210/http://sysdesignshowcase.broadcastengineering.com/ar/broadcasting_new_york_broadcasters |archive-date=June 4, 2008}}</ref>
[[File:Aerial view of the Pentagon during rescue operations post-September 11 attack.JPEG|thumb|A September 14 aerial view of [[the Pentagon]] during cleanup operations]]
The [[PATH (rail system)|PATH]] train system's [[World Trade Center station (PATH)|World Trade Center station]] was located under the complex and was demolished when the towers collapsed. The tunnels leading to [[Exchange Place station (PATH)|Exchange Place station]] in [[Jersey City, New Jersey|Jersey City]] were flooded with water.<ref>{{cite web|url=http://www.panynj.gov/drp/wtcpath/pathinfo.php|title=Downtown Restoration Program |publisher=The Port Authority of NY&NJ|date=January 11, 2009|access-date=February 7, 2018|url-status=dead|archive-url=https://web.archive.org/web/20090111002148/http://www.panynj.gov/drp/wtcpath/pathinfo.php|archive-date=January 11, 2009}}</ref> The station was rebuilt as the $4{{spaces}}billion [[World Trade Center Transportation Hub]], which reopened in March 2015.<ref>{{cite news |title=World Trade Center transportation hub, dubbed Oculus, opens to public |publisher=[[WABC-TV]] |date=March 3, 2016 |url=http://abc7ny.com/1229181/ |access-date=July 8, 2018 |archive-date=July 8, 2018 |archive-url=https://web.archive.org/web/20180708162414/http://abc7ny.com/1229181/ |url-status=live }}</ref><ref>{{cite web|url=http://www.panynj.gov/press-room/press-item.cfm?headLine_id=2353|title=Port Authority Announces Opening of World Trade Center Transportation Hub|date=January 19, 2016|publisher=Port Authority of New York and New Jersey|access-date=January 29, 2016|archive-date=February 3, 2016|archive-url=https://web.archive.org/web/20160203034610/http://www.panynj.gov/press-room/press-item.cfm?headLine_id=2353|url-status=dead}}</ref> The [[WTC Cortlandt station|Cortlandt Street station]] on the [[New York City Subway]]'s [[IRT Broadway–Seventh Avenue Line]] was also in close proximity to the World Trade Center complex, and the entire station, along with the surrounding track, was reduced to rubble.<ref>{{Cite news|url=https://www.nytimes.com/2002/01/04/nyregion/subway-line-in-attack-may-reopen-much-earlier.html|title=Subway Line in Attack May Reopen Much Earlier|last=Kennedy|first=Randy|date=January 4, 2002|work=The New York Times|access-date=February 7, 2018|issn=0362-4331|archive-date=April 23, 2014|archive-url=https://web.archive.org/web/20140423024227/http://www.nytimes.com/2002/01/04/nyregion/subway-line-in-attack-may-reopen-much-earlier.html|url-status=live}}</ref> The station was rebuilt and reopened to the public on September 8, 2018.<ref>{{cite news |title=WTC Cortlandt Subway Station Reopens for 1st Time Since 9/11 Attacks |url=https://www.nbcnewyork.com/news/local/WTC-Cortlandt-Subway-Station-Reopens-for-1st-Time-Since-9-11-Attacks-492777501.html |access-date=September 8, 2018 |publisher=[[WNBC-TV]] |agency=Associated Press |date=September 8, 2018 |archive-date=September 9, 2018 |archive-url=https://web.archive.org/web/20180909111234/https://www.nbcnewyork.com/news/local/WTC-Cortlandt-Subway-Station-Reopens-for-1st-Time-Since-9-11-Attacks-492777501.html |url-status=live }}</ref>

The Pentagon was extensively damaged, causing one section of the building to collapse.<ref>''The Pentagon Building Performance Report'', pp. ??{{page needed|date=September 2020}}</ref> As the [[American Airlines Flight 77|plane]] approached the Pentagon, its wings knocked down light poles and its right engine hit a power generator before crashing into the western side of the building.<ref>''Flight Path Study – American Airlines Flight 77'', pp. {{page needed|date=September 2020}}</ref><ref name="fdr">''American Airlines Flight 77 FDR Report'', pp. ??{{page needed|date=September 2020}}</ref> The plane hit the Pentagon at the first-floor level. The front part of the fuselage disintegrated on impact;{{sfnp|Goldberg et al.|2007|p=17}} debris from the tail section penetrated the furthest into the building, breaking through {{convert|310|ft|m|0}} of the three outermost of the building's five rings.{{sfnp|Goldberg et al.|2007|p=17}}<ref>{{cite news |last=Maclean |first=John N |title=America Under Attack: A chronicle of chaos and heroism at the Pentagon |url=https://www.washingtonpost.com/wp-dyn/content/article/2008/05/29/AR2008052903149.html |date=June 1, 2008 |newspaper=The Washington Post |access-date=September 3, 2011 |archive-date=December 18, 2014 |archive-url=https://web.archive.org/web/20141218104155/http://www.washingtonpost.com/wp-dyn/content/article/2008/05/29/AR2008052903149.html |url-status=live }}</ref>

=== Rescue efforts ===
{{Main|Rescue and recovery effort after the September 11 attacks on the World Trade Center}}
{{See also|List of emergency and first responder agencies that responded to the September 11 attacks}}
[[File:USACE Patrol Boat Hocking heads toward lower Manhattan on 9-11.jpg|thumb|Patrol Boat ''Hocking'' of the [[U.S. Army Corps of Engineers]] on its way to assist the site on September 11]]
The New York City Fire Department (FDNY) deployed more than 200 units (approximately half of the department) to the World Trade Center.<ref name="mckinsey-exec"/> Their efforts were supplemented by off-duty firefighters and [[emergency medical technician]]s.<ref name="mckinsey-ems">''McKinsey Report'', pp. 43–54, "Emergency Medical Service response
on September 11"</ref><ref name="mckinsey-exec">''McKinsey Report'', pp. 5–22, "Executive Summary"</ref><ref>''McKinsey Report'', pp. ??{{page needed|date=September 2020}}Exhibit 7, "Fire Apparatus Deployment on September 11"</ref> The New York City Police Department (NYPD) sent [[New York City Police Department Emergency Service Unit|its Emergency Service Units]] and other police personnel and deployed its aviation unit,<ref>''9/11 Commission Report'' (2004), pp. 291–292</ref> which determined that helicopter rescues from the towers were not feasible.<ref>''9/11 Commission Report'' (2004), pp. 286, 291–292</ref> Numerous police officers of the Port Authority Police Department&nbsp;(PAPD) also participated in rescue efforts.<ref>''9/11 Commission Report'' (2004), pp. 292–293.</ref> Once on the scene, the FDNY, the NYPD, and the PAPD did not coordinate efforts and performed redundant searches for civilians.<ref name="mckinsey-ems" />{{sfnp|Alavosius|Rodriquez|2005|pp=666–680}}

As conditions deteriorated, the NYPD aviation unit relayed information to police commanders, who issued orders for personnel to evacuate the towers; most NYPD officers were able to evacuate before the buildings collapsed.{{sfnp|Alavosius|Rodriquez|2005|pp=666–680}}<ref name="mckinsey-nypd">''McKinsey Report'', "NYPD", pp. ??{{page needed|date=September 2020}}</ref> With separate command posts set up and incompatible radio communications between the agencies, warnings were not passed along to FDNY commanders.<ref>''McKinsey Report'', pp. 7–9, 38</ref>

After the first tower collapsed, FDNY commanders issued evacuation warnings. Due to [[Radio communications during the September 11 attacks|malfunctioning radio repeater systems]], many firefighters never heard the evacuation orders. 9-1-1 dispatchers also received information from callers that was not passed along to commanders on the scene.<ref name="mckinsey-exec" />

== Reactions ==
{{Main|Reactions to the September 11 attacks}}
{{See also|Timeline for September following the September 11 attacks}}
The 9/11 attacks resulted in immediate responses, including [[U.S. government response to the September 11 attacks|domestic reactions]]; [[Closings and cancellations following the September 11 attacks|closings and cancellations]]; [[hate crime]]s; [[Reactions to the September 11 attacks|international responses]]; and [[U.S. military response during the September 11 attacks|military responses]]. Shortly after the attacks, the [[September 11th Victim Compensation Fund]] was created by an [[Act of Congress]].<ref>{{cite book |last=Feinberg |first=Kenneth |url=https://books.google.com/books?id=5j6N5LTz1N0C |title=Who Gets What: Fair Compensation after Tragedy and Financial Upheaval |year=2012 |publisher=[[PublicAffairs]] |isbn=978-1-58648-977-9 |location=New York |access-date=December 7, 2023 |archive-date=December 7, 2023 |archive-url=https://web.archive.org/web/20231207114436/https://books.google.com/books?id=5j6N5LTz1N0C |url-status=live }}</ref><ref>Feinberg, Kenneth. ''What is Life Worth?: The Unprecedented Effort to Compensate the Victims of 9/11'' (2005), Perseus Books Group.</ref> The purpose of the fund was to compensate the victims of the attacks and their families with their agreement not to file [[lawsuit]]s against the airlines involved.<ref>[https://web.archive.org/web/20041030084254/http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=107_cong_public_laws&docid=f:publ042.107 Government statistics concerning 9-11 compensation program]</ref> Legislation authorizes the fund to disburse a maximum of $7.375&nbsp;billion, including operational and administrative costs, of U.S. government funds.<ref>{{cite journal |date=October 3, 2018 |title=September 11th Victim Compensation Fund: Compensation of Claims |url=https://www.govinfo.gov/content/pkg/FR-2018-10-03/pdf/2018-21490.pdf |journal=Federal Register |volume=83 |issue=192 |pages=49946–49947 |accessdate=April 9, 2019 |archive-date=September 14, 2023 |archive-url=https://web.archive.org/web/20230914183424/https://www.govinfo.gov/content/pkg/FR-2018-10-03/pdf/2018-21490.pdf |url-status=live }}</ref> The fund was set to expire by 2020 but was in 2019 prolonged to allow claims to be filed until October 2090.<ref>{{Cite web |date=July 23, 2019 |title=Senate votes to permanently extend 9/11 victims fund |url=https://www.politico.com/story/2019/07/23/jon-stewart-9-11-victims-fund-vote-1427399 |access-date=November 25, 2023 |website=POLITICO |language=en |archive-date=November 25, 2023 |archive-url=https://web.archive.org/web/20231125133852/https://www.politico.com/story/2019/07/23/jon-stewart-9-11-victims-fund-vote-1427399 |url-status=live }}</ref><ref>{{Cite news |last1=Barrett |first1=Devlin |last2=Epstein |first2=Kayla |date=July 24, 2019 |title=Senate votes to extend 9/11 victims fund for first responders who've become sick since 2001 attacks |language=en-US |newspaper=[[The Washington Post]] |url=https://www.washingtonpost.com/national-security/senate-votes-to-extend-911-victims-fund-for-first-responders-whove-become-sick-since-2001-attacks/2019/07/23/c9fda47e-ad68-11e9-a0c9-6d2d7818f3da_story.html |access-date=November 25, 2023 |issn=0190-8286 |archive-date=May 29, 2022 |archive-url=https://web.archive.org/web/20220529121120/https://www.washingtonpost.com/national-security/senate-votes-to-extend-911-victims-fund-for-first-responders-whove-become-sick-since-2001-attacks/2019/07/23/c9fda47e-ad68-11e9-a0c9-6d2d7818f3da_story.html |url-status=live }}</ref>

=== Immediate response ===
{{Further|U.S. military response during the September 11 attacks}}
{{See also|Communication during the September 11 attacks}}
[[File:President George W. Bush Receives Information Regarding Terrorist Attacks.jpg|thumb|President [[George W. Bush]] is briefed in [[Sarasota, Florida]], where he learned of the attacks unfolding while visiting [[Emma E. Booker Elementary School|Emma E. Booker Elementary School<!-- MESSAGE TO POST-2094: When Paul J. Richards' copyright expires 70 years after his eventual death, this current image should be replaced with the one in the link below with a caption along the lines of:

"White House Chief of Staff Andrew Card informs President George W. Bush "A second plane hit the second tower. America is under attack" in Sarasota, Florida during a visit to Emma E. Booker Elementary School"
https://www.lowyinstitute.org/sites/default/files/GettyImages-150092234%20copy%202.jpeg

 -->]].]]
[[File:9 11 Terror Attacks Historical Pentagon Briefing.webm|thumb|start=02:16|alt=Rumsfeld in front of microphone flanked by suited politicians and a General, all with grim expressions|Eight hours after the attacks, [[United States Secretary of Defense|U.S. Secretary of Defense]] [[Donald Rumsfeld]] declares "The Pentagon is functioning".]]
At 8:32&nbsp;am, [[Federal Aviation Administration|FAA]] officials were notified Flight{{spaces}}11 had been hijacked and they, in turn, notified the [[North American Aerospace Defense Command]] (NORAD). NORAD scrambled two [[McDonnell Douglas F-15 Eagle|F-15s]] from [[Otis Air National Guard Base]] in Massachusetts; they were airborne by 8:53&nbsp;am. Because of slow and confused communication from FAA officials, NORAD had nine minutes' notice, and no notice about any of the other flights before they crashed.

After both of the Twin Towers had been hit, more fighters were scrambled from [[Joint Base Langley–Eustis|Langley Air Force Base]] in Virginia at 9:30&nbsp;am.<ref name="norad">{{cite web |title=We Have Some Planes |url=http://www.9-11commission.gov/report/911Report.pdf |website=The 911 Commission Report |publisher=911 Commission |access-date=September 9, 2011 |pages=20–42 |archive-date=October 9, 2022 |archive-url=https://ghostarchive.org/archive/20221009/http://www.9-11commission.gov/report/911Report.pdf |url-status=live }}</ref> At 10:20&nbsp;am, Vice President [[Dick Cheney]] issued orders to shoot down any commercial aircraft that could be positively identified as being hijacked. These instructions were not relayed in time for the fighters to take action.<ref name="norad"/><ref>{{cite news |title=Cheney: Order To Shoot Down Hijacked 9/11 Planes 'Necessary' |url=https://www.foxnews.com/politics/cheney-order-to-shoot-down-hijacked-9-11-planes-necessary/ |access-date=September 9, 2011 |publisher=Fox News Channel |date=September 4, 2011 |archive-date=September 24, 2015 |archive-url=https://web.archive.org/web/20150924140656/http://www.foxnews.com/politics/2011/09/04/cheney-order-to-shoot-down-hijacked-11-planes-necessary/ |url-status=live }}</ref><ref>{{cite news|last=Schrader|first=Esther|title=Cheney Gave Order to Shoot Down Jets|url=https://www.latimes.com/archives/la-xpm-2004-jun-18-na-cheney18-story.html|access-date=September 9, 2011|newspaper=Los Angeles Times|date=June 18, 2004|archive-date=August 11, 2011|archive-url=https://web.archive.org/web/20110811141540/http://articles.latimes.com/2004/jun/18/nation/na-cheney18|url-status=live}}</ref> Some fighters took to the air without live ammunition, knowing that to prevent the hijackers from striking their intended targets, the pilots might have to intercept and crash their fighters into the hijacked planes, possibly ejecting at the last moment.<ref>{{cite news |last=Hendrix |first=Steve |title=F-16 pilot was ready to give her life on Sept. 11 |url=https://www.washingtonpost.com/local/f-16-pilot-was-ready-to-give-her-life-on-sept-11/2011/09/06/gIQAMpcODK_story.html |newspaper=The Washington Post |date=September 8, 2011 |access-date=September 9, 2011 |archive-date=September 5, 2015 |archive-url=https://web.archive.org/web/20150905053526/http://www.washingtonpost.com/local/f-16-pilot-was-ready-to-give-her-life-on-sept-11/2011/09/06/gIQAMpcODK_story.html |url-status=live }}</ref>

For the first time in U.S. history, the emergency preparedness plan [[Security Control of Air Traffic and Air Navigation Aids]] (SCATANA) was invoked,<ref>{{cite web |author=Flight Data Center |title=NOTAMs/Flight Restrictions in Effect on September 13, 2001 |url=http://www.judicialwatch.org/archive/2007/Saudi%20Docs%202.pdf |publisher=Federal Bureau of Investigation |date=April 13, 2007 |page=15ff |access-date=January 17, 2010 |archive-date=February 25, 2014 |archive-url=https://web.archive.org/web/20140225071325/http://www.judicialwatch.org/archive/2007/Saudi%20Docs%202.pdf |url-status=live }}</ref> stranding tens of thousands of passengers across the world.<ref name="Commission">{{cite web |title=Wartime |url=http://www.9-11commission.gov/report/911Report_Ch10.htm |website=National Commission on Terrorists Attacks upon the United States |publisher=U.S. Congress |access-date=September 3, 2011 |archive-date=August 12, 2011 |archive-url=https://web.archive.org/web/20110812081229/http://www.9-11commission.gov/report/911Report_Ch10.htm |url-status=live }}</ref> [[Ben Sliney]], in his first day as the National Operations Manager of the [[Federal Aviation Administration|FAA]],<ref>{{cite news |last=Williams |first=Andrew |date=October 4, 2006 |title=60 Seconds: Ben Sliney |url=http://www.metro.co.uk/fame/interviews/article.html?in_article_id=20603&in_page_id=11 |work=[[Metro (British newspaper)|Metro]] |location=London |access-date=April 13, 2010 |archive-date=May 29, 2008 |archive-url=https://web.archive.org/web/20080529141832/http://www.metro.co.uk/fame/interviews/article.html?in_article_id=20603&in_page_id=11 |url-status=dead }}</ref> ordered that American airspace be closed to all international flights, causing about 500 flights to be turned back or redirected to other countries. Canada received 226 of the diverted flights and launched [[Operation Yellow Ribbon]] to deal with the large numbers of grounded planes and stranded passengers.<ref name="canadaflights">{{cite press release |title=Actions taken following September 11 terrorist attacks |date=December 11, 2001 |publisher=[[Transport Canada]] |url=http://www.tc.gc.ca/mediaroom/releases/nat/2001/01_h152e.htm |access-date=September 3, 2011 |archive-url= https://web.archive.org/web/20020415131425/http://www.tc.gc.ca/mediaroom/releases/nat/2001/01_h152e.htm |archive-date=April 15, 2002}}</ref>

The 9/11 attacks had immediate effects on the American people.<ref>{{cite journal |last=Stein |first=Howard F. |year=2003 |title=Days of Awe: September 11, 2001 and its Cultural Psychodynamics |journal=Journal for the Psychoanalysis of Culture and Society |volume=8 |issue=2 |pages=187–199 |doi=10.1353/psy.2003.0047|s2cid=144229311| issn = 1088-0763}}</ref> Police and rescue workers from around the country travelled to New York City to help recover bodies from the remnants of the Twin Towers.<ref>{{cite news |date=September 10, 2009 |title=Asthma Rates Up Among Ground Zero Workers |publisher=[[CBS News]] |agency=Associated Press |url=https://www.cbsnews.com/news/asthma-rates-up-among-ground-zero-workers/ |access-date=September 11, 2013 |archive-date=November 12, 2013 |archive-url=https://web.archive.org/web/20131112192716/http://www.cbsnews.com/2100-204_162-3207507.html |url-status=live }}</ref> Over 3,000 children lost a parent in the attacks.<ref>{{cite journal |last1=Coates |first1=S. |last2=Schechter |first2=D. |doi=10.1016/j.psc.2004.03.006 |title=Preschoolers' traumatic stress post-9/11: Relational and developmental perspectives |journal=Psychiatric Clinics of North America |volume=27 |issue=3 |pages=473–89 |year=2004 |pmid=15325488}}</ref> Blood donations across the U.S. surged in the weeks after 9/11.<ref>{{cite journal |last1=Glynn |first1=Simone A. |title=Effect of a National Disaster on Blood Supply and Safety: The September 11 Experience |year=2003 |journal=[[Journal of the American Medical Association]] |volume=289 |issue=17 |pmid=12734136 |doi=10.1001/jama.289.17.2246 |pages=2246–2253 |last2=Busch |first2=MP |last3=Schreiber |first3=GB |last4=Murphy |first4=EL |last5=Wright |first5=DJ |last6=Tu |first6=Y |last7=Kleinman |first7=SH |collaboration=Nhlbi Reds Study Group|doi-access=free}}</ref><ref>{{cite news |date=December 19, 2001 |title=Red Cross Woes |publisher=[[PBS]] |url=https://www.pbs.org/newshour/bb/business/july-dec01/redcross_12-19.html |access-date=September 3, 2011 |archive-url=https://web.archive.org/web/20110905071729/http://www.pbs.org/newshour/bb/business/july-dec01/redcross_12-19.html |archive-date=September 5, 2011 |url-status=dead}}</ref>

=== Domestic reactions ===
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| caption1          = President Bush addressing the nation from the [[White House]] at 8:30&nbsp;pm ET
| caption2          = Bush speaking to rescue workers at [[World Trade Center site|Ground Zero]] on September 14
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| caption2          = During a speech to a joint session of Congress, President George W. Bush pledges "to defend freedom against terrorism". September 20, 2001 (audio only).
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}}

Following the attacks, President George W. Bush's approval rating increased to 90%.<ref>{{cite news|url=http://www.gallup.com/poll/116500/Presidential-Approval-Ratings-George-Bush.aspx |title=Presidential Approval Ratings – George W. Bush |publisher=Gallup |access-date=September 4, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20090402045152/http://www.gallup.com/poll/116500/presidential-approval-ratings-george-bush.aspx |archive-date=April 2, 2009 }}</ref> On September 20, 2001, he addressed the nation and a joint session of Congress regarding the events, the rescue and recovery efforts, and his intended response to the attacks. [[Rudy Giuliani during the September 11 attacks|New York City mayor Rudy Giuliani's highly visible role]] resulted in praise in New York and nationally.<ref>{{cite magazine|last=Pooley|first=Eric|title=Mayor of the World|url=http://content.time.com/time/specials/packages/article/0,28804,2020227_2020306_2022358,00.html|magazine=[[Time (magazine)|Time]]|access-date=September 4, 2011|date=December 31, 2001|archive-date=September 30, 2013|archive-url=https://web.archive.org/web/20130930062651/http://content.time.com/time/specials/packages/article/0,28804,2020227_2020306_2022358,00.html|url-status=live}}</ref>

Many relief funds were immediately set up to provide [[Financial assistance following the September 11 attacks|financial assistance]] to the [[Casualties of the September 11 attacks|survivors of the attacks]] and the victims' families. By the deadline for victims' compensation on September 11, 2003, 2,833 applications had been received from the families of those killed.<ref>{{cite news |last=Barrett |first=Devlin |title=9/11 Fund Deadline Passes |publisher=CBS News |date=December 23, 2003 |url=https://www.cbsnews.com/news/9-11-fund-deadline-passes/ |access-date=September 4, 2011 |archive-date=August 26, 2011 |archive-url=https://web.archive.org/web/20110826063644/http://www.cbsnews.com/stories/2004/01/16/national/main593715.shtml |url-status=live }}</ref>

Contingency plans for the [[continuity of government]] and the evacuation of leaders were implemented soon after the attacks.<ref name="Commission"/> Congress was not told that the United States had been under a continuity of government status until February 2002.<ref>{{cite news |title='Shadow Government' News To Congress |publisher=CBS News |date=March 2, 2002 |url=https://www.cbsnews.com/news/shadow-government-news-to-congress/ |access-date=September 4, 2011 |archive-date=September 5, 2011 |archive-url=https://web.archive.org/web/20110905080451/http://www.cbsnews.com/stories/2002/03/01/attack/main502530.shtml |url-status=live }}</ref>

In the largest restructuring of the U.S. government in contemporary history, the United States enacted the [[Homeland Security Act of 2002]], creating the [[United States Department of Homeland Security|U.S. Department of Homeland Security]]. Congress also passed the [[USA PATRIOT Act]], saying it would help detect and prosecute terrorism and other crimes.<ref>{{cite web |title=The USA PATRIOT Act: Preserving Life and Liberty |publisher=[[United States Department of Justice]] |url= http://www.lifeandliberty.gov/highlights.htm |access-date=September 4, 2011 |archive-url=https://web.archive.org/web/20100102035036/http://www.justice.gov/archive/ll/highlights.htm|archive-date=January 2, 2010|url-status=dead}}</ref> Civil liberties groups have criticized the PATRIOT Act, saying it allows law enforcement to invade citizens' privacy and that it eliminates judicial oversight of law enforcement and domestic intelligence.<ref name="ACLUAdv">{{cite press release |url=https://www.aclu.org/national-security/uncle-sam-asks-what-hell-going-herein-new-aclu-print-and-radio-advertisements |title=Uncle Sam Asks: "What The Hell Is Going On Here?" in New ACLU Print and Radio Advertisements |publisher=[[American Civil Liberties Union]] |date=September 3, 2003 |access-date=April 10, 2012 |archive-date=June 3, 2012 |archive-url=https://web.archive.org/web/20120603123234/http://www.aclu.org/national-security/uncle-sam-asks-what-hell-going-herein-new-aclu-print-and-radio-advertisements |url-status=live }}</ref><ref>{{cite news |last=Eggen |first=Dan |date=September 30, 2004 |newspaper=The Washington Post |title=Key Part of Patriot Act Ruled Unconstitutional |url=https://www.washingtonpost.com/wp-dyn/articles/A59626-2004Sep29.html |access-date=September 4, 2011 |archive-date=October 20, 2013 |archive-url=https://web.archive.org/web/20131020081006/http://www.washingtonpost.com/wp-dyn/articles/A59626-2004Sep29.html |url-status=live }}</ref><ref>{{cite news |url=http://www.cnn.com/2007/US/law/09/26/patriot.act/index.html |title=Federal judge rules 2 Patriot Act provisions unconstitutional |access-date=September 4, 2011 |date=September 26, 2007 |publisher=CNN |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172324/http://www.cnn.com/2007/US/law/09/26/patriot.act/index.html%20 |url-status=live }}</ref>

To effectively combat future acts of terrorism, the [[National Security Agency]] (NSA) was given broad powers. NSA commenced [[NSA warrantless surveillance controversy|warrantless surveillance]] of telecommunications, which was sometimes criticized as permitting the agency "to eavesdrop on telephone and e-mail communications between the United States and people overseas without a warrant".<ref>{{cite news |last1=VandeHei |first1=Jim |last2=Eggen |first2=Dan |title=Cheney Cites Justifications For Domestic Eavesdropping |newspaper=The Washington Post |date=January 5, 2006 |url=https://www.washingtonpost.com/wp-dyn/content/article/2006/01/04/AR2006010400973.html |access-date=September 4, 2011 |archive-date=August 20, 2011 |archive-url=https://web.archive.org/web/20110820073716/http://www.washingtonpost.com/wp-dyn/content/article/2006/01/04/AR2006010400973.html |url-status=live }}</ref> In response to requests by intelligence agencies, the [[United States Foreign Intelligence Surveillance Court]] permitted an expansion of powers by the U.S. government in seeking, obtaining, and sharing information on U.S. citizens as well as non-Americans around the world.<ref>{{cite news |last1=Savage |first1=Charlie |last2=Poitras |first2=Laura |title=How a Court Secretly Evolved, Extending U.S. Spies' Reach |work=The New York Times |date=March 11, 2014 |url=https://www.nytimes.com/2014/03/12/us/how-a-courts-secret-evolution-extended-spies-reach.html |access-date=March 13, 2014 |archive-date=March 12, 2014 |archive-url=https://web.archive.org/web/20140312220916/http://www.nytimes.com/2014/03/12/us/how-a-courts-secret-evolution-extended-spies-reach.html |url-status=live }}</ref>

==== Hate crimes ====
{{See also|Islamophobic incidents|Persecution of Muslims}}
Six days after the attacks, President Bush made a public appearance at [[Islamic Center of Washington|Washington, D.C.'s largest Islamic Center]] where he acknowledged the "incredibly valuable contribution" of [[Islam in the United States|American Muslims]] and called for them "to be treated with respect".<ref>{{cite news |last=Freedman |first=Samuel G. |title=Six Days After 9/11, Another Anniversary Worth Honoring |url=https://www.nytimes.com/2012/09/08/us/on-religion-six-days-after-9-11-another-anniversary-worth-honoring.html |work=The New York Times |date=September 7, 2012 |access-date=March 12, 2015 |archive-date=November 6, 2019 |archive-url=https://web.archive.org/web/20191106125316/https://www.nytimes.com/2012/09/08/us/on-religion-six-days-after-9-11-another-anniversary-worth-honoring.html |url-status=live }}</ref> Numerous incidents of [[harassment]] and [[hate crime]]s against [[Muslims]] and [[South Asian ethnic groups|South Asians]] were reported in the days following the attacks.<ref>{{cite web |url= http://www.nyc.gov/html/cchr/html/report.html |title=New York City Commission on Human Rights |publisher=Nyc.gov |url-status=dead |archive-url=https://web.archive.org/web/20040203071912/http://www.nyc.gov/html/cchr/html/report.html |archive-date=February 3, 2004 |access-date=May 29, 2014}}</ref><ref>{{cite news|url=http://www.indianexpress.com/news/post9-11-us-policies-created-atmosphere-of-fear-for-south-asians/836936|title=Post-9/11, US policies created atmosphere of fear for South Asians|website=The Indian Express|date=August 25, 2011|access-date=October 23, 2011|archive-date=May 26, 2020|archive-url=https://web.archive.org/web/20200526183307/http://archive.indianexpress.com/news/post9-11-us-policies-created-atmosphere-of-fear-for-south-asians/836936|url-status=live}}</ref><ref name="Hate">{{cite news |title=Hate crime reports up in wake of terrorist attacks |publisher=CNN|date=September 17, 2001 |url=http://archives.cnn.com/2001/US/09/16/gen.hate.crimes |url-status=dead |archive-url=https://web.archive.org/web/20051127025019/http://archives.cnn.com/2001/US/09/16/gen.hate.crimes/ |archive-date=November 27, 2005 |access-date=May 29, 2014}}</ref>

[[Sikh]]s were also targeted due to their use of [[turban]]s, which are stereotypically associated with Muslims. There were reports of attacks on mosques and other religious buildings (including the firebombing of a [[Hindu temple]]), and assaults on individuals, including one murder: [[Murder of Balbir Singh Sodhi|Balbir Singh Sodhi]], a Sikh mistaken for a Muslim, who was fatally shot on September 15, 2001, in [[Mesa, Arizona]].<ref name="Hate" /> Two dozen members of Osama bin Laden's family were urgently evacuated out of the country on a private charter plane under FBI supervision three days after the attacks.<ref>{{cite news|url=https://www.cbsnews.com/news/bin-laden-family-evacuated/|title=Bin Laden Family Evacuated|publisher=CBS News|access-date=January 30, 2019|archive-date=April 11, 2020|archive-url=https://web.archive.org/web/20200411091619/https://www.cbsnews.com/news/bin-laden-family-evacuated/|url-status=live}}</ref>

According to an academic study, people perceived to be [[Ethnic groups in the Middle East|Middle Eastern]] were as likely to be victims of hate crimes as followers of [[Islam]] during this time. The study also found a similar increase in hate crimes against people who may have been perceived as Muslims, [[Arabs]], and others thought to be of Middle Eastern origin.<ref>{{cite web |publisher=[[Ball State University]] |url=http://www.bsu.edu/news/article/0,1370,-1019-12850,00.html |title=Many minority groups were victims of hate crimes after 9-11 |date=October 9, 2003 |url-status=dead |archive-url=https://web.archive.org/web/20081211050839/http://www.bsu.edu/news/article/0%2C1370%2C-1019-12850%2C00.html |archive-date=December 11, 2008 |access-date=May 29, 2014}}</ref> A report by the South Asian American advocacy group South Asian Americans Leading Together documented media coverage of 645 bias incidents against Americans of South Asian or Middle Eastern descent between September 11 and 17, 2001. Crimes such as vandalism, arson, assault, shootings, harassment, and threats in numerous places were documented.<ref>{{cite web |title=American Backlash: Terrorist Bring War Home in More Ways Than One |url=http://www.saalt.org/attachments/1/American%20Backlash%20report.pdf |access-date=May 29, 2014 |year=2003 |publisher=SAALT |archive-url=https://web.archive.org/web/20101203140832/http://static.911digitalarchive.org/REPOSITORY/OTHER_OBJECTS/6object.pdf |archive-date=December 3, 2010 |url-status=dead}}</ref><ref>{{cite news |last=Thayil |first=Jeet|date=October 12, 2001 |title=645 racial incidents reported in week after September 11 |newspaper=[[India Abroad]] |url=http://www.highbeam.com/doc/1P1-79281024.html|url-status=dead|archive-url=https://web.archive.org/web/20110511211812/http://www.highbeam.com/doc/1P1-79281024.html |archive-date=May 11, 2011}}</ref> Women wearing [[hijab]] were also targeted.<ref name="HRW not enemy">{{Cite web |title=We Are Not the Enemy: Hate Crimes Against Arabs, Muslims, and Those Perceived to be Arab or Muslim after September 11 |url=https://www.hrw.org/reports/2002/usahate/usa1102-04.htm |url-status=live |archive-url=https://web.archive.org/web/20220522192143/https://www.hrw.org/reports/2002/usahate/usa1102-04.htm |archive-date=May 22, 2022 |date=November 2002 |access-date=June 7, 2022 |publisher=[[Human Rights Watch]]}}</ref>

==== Discrimination and racial profiling ====
{{Further|Detentions following the September 11 attacks|Islamophobia in the United States|Flying while Muslim}}
{{See also|Airport racial profiling in the United States}}
A poll of [[Arab Americans|Arab-Americans]] in May 2002 found that 20% had personally experienced discrimination since September 11. A July 2002 poll of Muslim Americans found that 48% believed their lives had changed for the worse since September 11, and 57% had experienced an act of bias or discrimination.<ref name="HRW not enemy" /> Following the September 11 attacks, many [[Pakistani Americans]] identified themselves as Indians to avoid potential discrimination and obtain jobs.<ref>{{cite news |title=Pakistanis pose as Indians after NY bomb scare |url=https://www.reuters.com/article/us-timessquare-backlash/pakistanis-pose-as-indians-after-ny-bomb-scare-idUSTRE64655Y20100507 |publisher=[[Reuters]] |access-date=March 23, 2020 |date=May 7, 2010 |archive-date=January 14, 2021 |archive-url=https://web.archive.org/web/20210114111303/https://www.reuters.com/article/us-timessquare-backlash/pakistanis-pose-as-indians-after-ny-bomb-scare-idUSTRE64655Y20100507 |url-status=live }}</ref>

By May 2002, there were 488 complaints of [[Employment discrimination in the United States|employment discrimination]] reported to the U.S. Equal Employment Opportunity Commission (EEOC). 301 of those were complaints from people fired from their jobs. Similarly, by June 2002, the U.S. Department of Transportation (DOT) had investigated 111 September 11th-related complaints from airline passengers purporting that their religious or ethnic appearance caused them to be singled out at security screenings, and an additional 31 complaints from people who alleged they were blocked from boarding aeroplanes on the same grounds.<ref name="HRW not enemy" />

==== Muslim American response ====
{{See also|Muslim attitudes towards terrorism|Peace in Islamic philosophy}}
Muslim organizations in the United States were swift to condemn the attacks and called "upon [[Muslim Americans]] to come forward with their skills and resources to help alleviate the sufferings of the affected people and their families".<ref>{{cite web |last=American Muslim Leaders |title=Muslim Americans Condemn Attack |publisher=ISNA |url=http://www.islamicity.com/articles/Articles.asp?ref=AM0109-335 |access-date=September 4, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172342/https://www.islamicity.org/?AspxAutoDetectCookieSupport=1 |url-status=live }}</ref> These organizations included the [[Islamic Society of North America]], American Muslim Alliance, [[American Muslim Council]], [[Council on American-Islamic Relations]], [[Islamic Circle of North America]], and the Shari'a Scholars Association of North America. Along with monetary donations, many Islamic organizations launched blood drives and provided medical assistance, food, and shelter for victims.<ref>{{cite news|last=Beaulieu |first=Dan |title=Muslim groups around world condemn the killing of innocents |publisher=Agence France Presse |language=en |date=September 12, 2001}}</ref><ref>{{cite news|last=Davis |first=Joyce M. |title=Muslims condemn attacks, insist Islam not violent against innocents |agency=Knight Ridder Washington Bureau |date=September 13, 2001}}</ref><ref>{{cite news|last=Witham |first=Larry |title=Muslim groups decry attacks; No cause justifies the 'immoral' act, U.S. councils say |work=The Washington Times |date=September 12, 2001}}</ref>

==== Interfaith efforts ====
Curiosity about Islam increased after the attacks. As a result, many mosques and Islamic centres began holding open houses and participating in outreach efforts to educate non-Muslims about the faith. In the first 10 years after the attacks, [[Interfaith dialogue|interfaith]] community service increased from 8 to 20 percent and the percentage of U.S. congregations involved in interfaith worship doubled from 7 to 14 percent.<ref>{{Cite news|date=September 8, 2011|title=From fear of Islam to outreach: how 9/11 prompted interfaith efforts|work=The Christian Science Monitor|url=https://www.csmonitor.com/USA/Society/2011/0908/From-fear-of-Islam-to-outreach-how-9-11-prompted-interfaith-efforts|access-date=August 27, 2021|issn=0882-7729|archive-date=August 27, 2021|archive-url=https://web.archive.org/web/20210827153610/https://www.csmonitor.com/USA/Society/2011/0908/From-fear-of-Islam-to-outreach-how-9-11-prompted-interfaith-efforts|url-status=live}}</ref>

=== International reactions ===
[[File:Vladimir Putin in the United States 13-16 November 2001-54.jpg|thumb|[[President of Russia]] [[Vladimir Putin]] (''right'') with [[Lyudmila Putina|his wife]] (''center'') at a commemoration service in New York City on November 16]]
The attacks were denounced by mass media and governments worldwide. Nations offered pro-American support and solidarity.<ref>{{cite magazine|last=Hertzberg|first=Hendrik|date=September 11, 2006|title=Lost love|url=http://www.newyorker.com/archive/2006/09/11/060911ta_talk_hertzberg|url-status=live|magazine=[[The New Yorker]]|archive-url=https://web.archive.org/web/20110606070654/http://www.newyorker.com/archive/2006/09/11/060911ta_talk_hertzberg|archive-date=June 6, 2011|access-date=September 4, 2011}}</ref> Leaders in most Middle Eastern countries, as well as Libya and Afghanistan, condemned the attacks. Iraq was a notable exception, with an immediate official statement that "the American cowboys are reaping the fruit of their crimes against humanity".<ref>{{cite news|date=September 12, 2001|title=Attacks draw mixed response in Mideast|publisher=[[CNN]]|url=http://archives.cnn.com/2001/WORLD/europe/09/12/mideast.reaction/index.html|url-status=dead|access-date=May 29, 2014|archive-url=https://web.archive.org/web/20070813060324/http://archives.cnn.com/2001/WORLD/europe/09/12/mideast.reaction/index.html|archive-date=August 13, 2007}}</ref> The government of Saudi Arabia officially condemned the attacks, but privately many Saudis favored bin Laden's cause.<ref>{{cite book|last1=Summers|first1=Anthony|url=https://archive.org/details/eleventhdayfulls0000summ|title=The Eleventh Day: The Full Story of 9/11 and Osama bin Laden|last2=Swan|first2=Robbyn|publisher=[[Ballantine Books]]|year=2011|isbn=978-1-4000-6659-9|location=New York|page=[https://archive.org/details/eleventhdayfulls0000summ/page/403 403]|url-access=registration}}</ref><ref name="The Kingdom and the Towers">{{cite web |last1=Summers |first1=Anthony |last2=Swan |first2=Robbyn |date=June 30, 2011 |title=The Kingdom and the Towers |url=http://www.vanityfair.com/politics/features/2011/08/9-11-2011-201108 |url-status=live |archive-url=https://web.archive.org/web/20110901235354/http://www.vanityfair.com/politics/features/2011/08/9-11-2011-201108 |archive-date=September 1, 2011 |access-date=September 4, 2011 |website=[[Vanity Fair (magazine)|Vanity Fair]]}}</ref>

Although [[Palestinian Authority]] (PA) president [[Yasser Arafat]] also condemned the attacks, there were reports of celebrations of disputed size in the [[West Bank]], [[Gaza Strip]], and [[East Jerusalem]].<ref>{{cite news|date=September 12, 2001|title=In pictures: Atrocities' aftermath|language=en-GB|publisher=[[BBC News]]|url=http://news.bbc.co.uk/2/hi/americas/1538664.stm|access-date=September 12, 2019|archive-date=July 26, 2008|archive-url=https://web.archive.org/web/20080726224706/http://news.bbc.co.uk/1/hi/world/americas/1538664.stm|url-status=live}}</ref><ref>{{cite book|last=Porter|first=Patrick|url=https://books.google.com/books?id=VE5yDwAAQBAJ&pg=PA139|title=Blunder: Britain's War in Iraq|publisher=[[Oxford University Press]]|year=2018|isbn=978-0-19-880796-4|page=139|access-date=September 12, 2019|archive-date=December 7, 2023|archive-url=https://web.archive.org/web/20231207114404/https://books.google.com/books?id=VE5yDwAAQBAJ&pg=PA139#v=onepage&q&f=false|url-status=live}}</ref> Palestinian leaders discredited news broadcasters that justified the attacks or showed celebrations,<ref name="fox1">{{cite news |url=https://www.foxnews.com/story/arafat-horrified-by-attacks-but-thousands-of-palestinians-celebrate-rest-of-world-outraged |publisher=Fox News |title=Arafat Horrified by Attacks, but Thousands of Palestinians Celebrate; Rest of World Outraged |date=September 12, 2001 |access-date=April 17, 2008 |archive-url=https://web.archive.org/web/20080413170546/http://www.foxnews.com/story/0,2933,34187,00.html |archive-date=April 13, 2008 |url-status=live  }}</ref> and the Authority claimed such celebrations do not represent the Palestinians' sentiment.<ref>Palestinian Authority has muzzled coverage of Palestinian celebrations' (Middle East Newsline)<br />'Israel to AP: Release film of Palestinian celebrations' (Jerusalem Post/The Associated Press)<br />'Bin-Laden Poster Seen at Gaza Rally' (The Associated Press).</ref><ref name="FOX_Quash">{{cite news |last=Donaldson |first=Catherine |url=http://www.foxnews.com/story/0,2933,34346,00.html |title='Palestinian Officials Quash Pictures of Arab Celebrations' by Catherine Donaldson-Evans |publisher=Fox News |date=September 13, 2001 |access-date=September 11, 2011 |archive-url=https://web.archive.org/web/20110505074246/http://www.foxnews.com/story/0,2933,34346,00.html |archive-date=May 5, 2011 |url-status=live}}</ref> Footage by CNN{{vague|date=May 2020}} and other news outlets were suggested by a report originating at a Brazilian university to be from 1991; this was later proven to be a false accusation.<ref>{{cite news|url=http://archives.cnn.com/2001/US/09/20/cnn.statement/|title=CNN statement about false claim it used old video – September 20, 2001|date=April 16, 2008|archive-url=https://web.archive.org/web/20080416104012/http://archives.cnn.com/2001/US/09/20/cnn.statement/|access-date=September 12, 2019|archive-date=April 16, 2008}}</ref><ref>{{cite web|title=Palestinians Dancing in the Street|url=https://www.snopes.com/fact-check/false-footaging/|access-date=September 12, 2019|website=[[Snopes]]|date=March 9, 2008|language=en-US|archive-date=June 30, 2022|archive-url=https://web.archive.org/web/20220630180736/https://www.snopes.com/fact-check/false-footaging/|url-status=live}}</ref> As in the United States, the aftermath of the attacks saw tensions increase in other countries between Muslims and non-Muslims.<ref>{{cite news |title=Muslim community targets racial tension |url=http://news.bbc.co.uk/2/hi/uk_news/1551868.stm |publisher=BBC News |date=September 19, 2001 |access-date=April 11, 2012 |archive-date=March 21, 2012 |archive-url=https://web.archive.org/web/20120321022930/http://news.bbc.co.uk/2/hi/uk_news/1551868.stm |url-status=live }}</ref>

[[United Nations Security Council Resolution 1368]] condemned the attacks and expressed readiness to take all necessary steps to respond and combat terrorism in accordance with their [[Chapter VII of the United Nations Charter|Charter]].<ref name="SecCounc">{{cite web|title=Security Council Condemns, 'In Strongest Terms', Terrorist Attacks on the United States|publisher=United Nations|date=September 12, 2001|url=https://www.un.org/News/Press/docs/2001/SC7143.doc.htm|access-date=September 11, 2006|quote=The Security Council today, following what it called yesterday's "horrifying terrorist attacks" in New York, Washington, D.C., and Pennsylvania, unequivocally condemned those acts, and expressed its deepest sympathy and condolences to the victims and their families and to the people and Government of the United States.|archive-date=September 9, 2006|archive-url=https://web.archive.org/web/20060909162055/http://www.un.org/News/Press/docs/2001/SC7143.doc.htm|url-status=live}}</ref> Numerous countries introduced anti-terrorism legislation and froze bank accounts they suspected of Al-Qaeda ties.<ref>{{cite web|last=Hamilton|first=Stuart|date=August 24, 2002|title=September 11, the Internet, and the effects on information provision in Libraries|url=http://archive.ifla.org/IV/ifla68/papers/156-079e.pdf|access-date=September 4, 2011|publisher=[[International Federation of Library Associations and Institutions]]|archive-date=September 11, 2011|archive-url=https://web.archive.org/web/20110911170808/http://archive.ifla.org/IV/ifla68/papers/156-079e.pdf|url-status=live}}</ref><ref>{{cite web|title=G8 counter-terrorism cooperation since September 11 backgrounder|url=http://www.g8.fr/evian/english/navigation/g8_documents/archives_from_previous_summits/kananaskis_summit_-_2002/g8_counter-terrorism_cooperation_since_september_11th_backgrounder.html|url-status=dead|archive-url=https://web.archive.org/web/20110927084019/http://www.g8.fr/evian/english/navigation/g8_documents/archives_from_previous_summits/kananaskis_summit_-_2002/g8_counter-terrorism_cooperation_since_september_11th_backgrounder.html|archive-date=September 27, 2011|access-date=September 4, 2011|publisher=[[Group of Eight]]}}</ref> Law enforcement and intelligence agencies in a number of countries arrested alleged terrorists.<ref>{{cite news |last=Walsh |first=Courtney C |title=Italian police explore Al Qaeda links in cyanide plot |website=The Christian Science Monitor |date=March 7, 2002 |url=http://www.csmonitor.com/2002/0307/p07s02-woeu.html |access-date=September 4, 2011 |archive-date=September 9, 2011 |archive-url=https://web.archive.org/web/20110909191322/http://www.csmonitor.com/2002/0307/p07s02-woeu.html |url-status=live }}</ref><ref>{{cite news |title=SE Asia unites to smash militant cells |publisher=CNN |date=May 8, 2002 |url=http://edition.cnn.com/2002/WORLD/asiapcf/southeast/05/07/seasia.terror.pact/ |access-date=September 4, 2011 |archive-date=August 15, 2011 |archive-url=https://web.archive.org/web/20110815074324/http://edition.cnn.com/2002/WORLD/asiapcf/southeast/05/07/seasia.terror.pact/ |url-status=live }}</ref>

British Prime Minister [[Tony Blair]] said Britain stood "shoulder to shoulder" with the United States.<ref>{{cite news |title=Blair's statement in full |url=http://news.bbc.co.uk/1/hi/uk_politics/1538551.stm |publisher=BBC News |date=September 11, 2001 |access-date=August 23, 2021 |archive-date=March 7, 2022 |archive-url=https://web.archive.org/web/20220307034034/http://news.bbc.co.uk/1/hi/uk_politics/1538551.stm |url-status=live }}</ref> In a speech to Congress nine days after the attacks, which Blair attended as a guest, President Bush declared "America has no truer friend than Great Britain".<ref>{{cite web|title=President Declares 'Freedom at War with Fear' |url=https://georgewbush-whitehouse.archives.gov/news/releases/2001/09/20010920-8.html |publisher=The White House |access-date=August 25, 2016 |date=September 20, 2001 |url-status=dead |archive-url=https://web.archive.org/web/20080225062850/http://georgewbush-whitehouse.archives.gov/news/releases/2001/09/20010920-8.html |archive-date=February 25, 2008 }}</ref> Subsequently, Prime Minister Blair embarked on two months of diplomacy to rally international support for military action; he held 54 meetings with world leaders.<ref>{{cite news |title=Tony Blair's allegiance to George Bush laid bare |url=https://www.standard.co.uk/news/tony-blairs-corrosive-allegiance-to-george-bush-laid-bare-for-the-first-time-6668892.html |work=Evening Standard |location=London |date=October 27, 2007 |access-date=August 23, 2021 |archive-date=January 13, 2021 |archive-url=https://web.archive.org/web/20210113071246/https://www.standard.co.uk/news/tony-blairs-corrosive-allegiance-to-george-bush-laid-bare-for-the-first-time-6668892.html |url-status=live }}</ref>

The U.S. set up the [[Guantanamo Bay detention camp]] to hold inmates they defined as "[[illegal enemy combatants]]". The legitimacy of these detentions has been questioned by the [[European Union]] and human rights organizations.<ref>{{cite news |title=Euro MPs urge Guantanamo closure |url=http://news.bbc.co.uk/2/hi/americas/5074216.stm |publisher=BBC News |date=June 13, 2006 |access-date=September 4, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172515/http://news.bbc.co.uk/2/hi/americas/5074216.stm%20 |url-status=live }}</ref><ref>{{cite web |last=Mendez |first=Juan E. |author-link=Juan E. Méndez |date=March 13, 2002 |title=Detainees in Guantanamo Bay, Cuba; Request for Precautionary Measures, Inter-Am. C.H.R |url=http://www1.umn.edu/humanrts/cases/guantanamo-2003.html |publisher=[[University of Minnesota]] |access-date=September 4, 2011 |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172520/http://hrlibrary.umn.edu/cases/guantanamo-2003.html%20 |url-status=live }}</ref><ref>{{cite web |title=USA: Release or fair trials for all remaining Guantánamo detainees |url=https://www.amnesty.org/press-releases/2008/05/usa-release-or-fair-trials-all-remaining-guantc3a1namo-detainees-20080502/ |publisher=Amnesty International |date=May 2, 2008 |access-date=September 4, 2011 |archive-date=December 7, 2023 |archive-url=https://web.archive.org/web/20231207114425/https://www.amnesty.org/en/latest/press-release/2008/05/usa-release-or-fair-trials-all-remaining-guantc3a1namo-detainees-20080502/ |url-status=live }}</ref>

On September 25, 2001, [[Iran]]'s president [[Mohammad Khatami]], meeting British Foreign Secretary [[Jack Straw]], said: "Iran fully understands the feelings of the Americans about the terrorist attacks in New York and Washington on September 11". He said although the American administrations had been at best indifferent about terrorist operations in Iran, the Iranians felt differently and had expressed their sympathetic feelings with bereaved Americans in the tragic incidents in the two cities. He also stated that "Nations should not be punished in place of terrorists".<ref>[https://web.archive.org/web/20020503200608/http://www.president.ir/cronicnews/1380/8007/800703/800703.htm P.I.R.I News Headlines (Tue 80/07/03 A.H.S)]. The Official Site of the Office of the President of Iran. [http://president.ir/en Official website of the President of the Islamic Republic of Iran]. September 25, 2001. Permanent Archived Link. The original page and URL are not available online now. ([https://web.archive.org/web/20010926214218/http://www.president.ir/ Website's Homepage at that time (Title: Presidency of The Islamic Republic of Iran, The Official Site)])</ref>

According to [[Radio Farda]]'s website, when the news of the attacks was released, some Iranian citizens gathered in front of the Embassy of Switzerland in Tehran, which serves as the protecting power of the United States in Iran, to express their sympathy, and some of them lit candles as a symbol of mourning. Radio Farda's website also states that in 2011, on the anniversary of the attacks, the [[United States Department of State]] published a post on its blog, in which the Department thanked the Iranian people for their sympathy and stated that it would never forget Iranian people's kindness.<ref>{{cite news |url=http://www.radiofarda.com/content/f12_us_state_department_thanks_iranian_sympathy_with_sept_11_victims_in_2001/24324962.html |title=تشکر وزارت خارجه آمریکا از همدردی ایرانیان با قربانیان ۱۱ سپتامبر |language=fa |website=[[Radio Farda]] |date=September 11, 2011 |archive-url=https://web.archive.org/web/20120121163708/http://www.radiofarda.com/content/f12_us_state_department_thanks_iranian_sympathy_with_sept_11_victims_in_2001/24324962.html |archive-date=January 21, 2012 |access-date=June 30, 2016 |url-status=live }} [https://translate.google.com/translate?&sl=fa&tl=en&u=http%3A%2F%2Fwww.radiofarda.com%2Fcontent%2Ff12_us_state_department_thanks_iranian_sympathy_with_sept_11_victims_in_2001%2F24324962.html A mechanized Translation by Google Translate is available here] {{Webarchive|url=https://web.archive.org/web/20210813021914/https://translate.google.com/translate?&sl=fa&tl=en&u=http%3A%2F%2Fwww.radiofarda.com%2Fcontent%2Ff12_us_state_department_thanks_iranian_sympathy_with_sept_11_victims_in_2001%2F24324962.html |date=August 13, 2021 }}.</ref> After the attacks, both the President<ref>[http://en.isna.ir/news/8008-04338/Iran-s-President-Says-Muslims-Reject-bin-Laden-s-Islam "Iran's President Says Muslims Reject bin Laden's 'Islam'"]. [[Iranian Students News Agency]]. November 10, 2001 / 17:07. [https://web.archive.org/web/20160918154504/http://en.isna.ir/news/8008-04338/Iran-s-President-Says-Muslims-Reject-bin-Laden-s-Islam Permanent Archived Link]. Retrieved and archived on September 18, 2016, 15:45:04 UTC.</ref><ref>[http://www.ynetnews.com/articles/0,7340,L-3302180,00.html Ynetnews News – Khatami slams bin Laden, defends Hizbullah]. [[Ynetnews]]. November 9, 2006. [https://web.archive.org/web/20160908183108/http://www.ynetnews.com/articles/0,7340,L-3302180,00.html Permanent Archived Link]. Retrieved and archived on September 8, 2016; 18:31:08 UTC.</ref> and the Supreme Leader of Iran condemned the attacks. The [[BBC]] and ''[[Time (magazine)|Time]]'' magazine published reports on holding candlelit vigils for the victims of Iranian citizens on their websites.<ref>{{cite news |last=Corera |first=Gordon |title=Iran's gulf of misunderstanding with US |url=http://news.bbc.co.uk/1/hi/world/middle_east/5377914.stm |publisher=BBC News |date=September 25, 2006 |access-date=May 22, 2010 |archive-date=February 15, 2009 |archive-url=https://web.archive.org/web/20090215064710/http://news.bbc.co.uk/1/hi/world/middle_east/5377914.stm |url-status=live }} [https://web.archive.org/web/20160404184211/http://news.bbc.co.uk/2/hi/middle_east/5377914.stm Permanent Archived Link].</ref><ref>[https://web.archive.org/web/20101115094604/http://www.time.com/time/europe/photoessays/vigil/2.html Iran mourns America's dead] ''Time''</ref> According to ''[[Politico#Politico Magazine|Politico Magazine]]'', following the attacks, [[Ali Khamenei]], the Supreme Leader of Iran, "suspended the usual '[[Death to America]]' chants at [[Jumu'ah|Friday prayers]]" temporarily.<ref name="Politico 2013-11-19">{{cite news |last=Slavin |first=Barbara |title=34 Years of Getting to No with Iran |url=https://www.politico.com/magazine/story/2013/11/a-failure-to-communicate-100052.html |website=[[Politico|Politico Magazine]] |date=November 19, 2013 |access-date=July 4, 2016 |archive-url=https://web.archive.org/web/20140129195150/http://www.politico.com/magazine/story/2013/11/a-failure-to-communicate-100052.html |archive-date=January 29, 2014}}</ref>

=== Military operations ===
{{further|War on terror|US invasion of Afghanistan}}{{Events leading to the Iraq War}}
At 2:40&nbsp;pm on September 11, [[United States Secretary of Defense|Secretary of Defense]] [[Donald Rumsfeld]] was issuing orders to his aides to look for evidence of Iraqi involvement. According to notes taken by senior policy official [[Stephen Cambone]], Rumsfeld asked for, "Best info fast. Judge whether they are good enough to hit S.H. [Saddam Hussein] at the same time. Not only UBL" [Osama bin Laden].<ref>{{cite episode |title=Bush's War |access-date=September 4, 2011 |series=Frontline |series-link=Frontline (U.S. TV series) |credits=Written, produced and directed by [[Michael Kirk]], produced and reported by Jim Gilmore |network=PBS |station=WGBH |location=Boston |date=March 24–25, 2008 |time=8:40 |transcript=Transcript |transcript-url=https://www.pbs.org/wgbh/pages/frontline/bushswar/etc/script.html |url=https://www.pbs.org/wgbh/pages/frontline/bushswar/ |archive-date=December 11, 2018 |archive-url=https://web.archive.org/web/20181211110930/https://www.pbs.org/wgbh/pages/frontline/bushswar/ |url-status=live }}</ref>

In a meeting at [[Camp David]] on September 15 the Bush administration rejected the idea of attacking [[Ba'athist Iraq|Iraq]] in response to the September 11 attacks.<ref>{{cite web|url=http://avalon.law.yale.edu/sept11/911Report.pdf |title=The 9/11 Commission Report |work=[[Avalon Project]] |archive-url=https://web.archive.org/web/20151123013421/http://avalon.law.yale.edu/sept11/911Report.pdf |archive-date=November 23, 2015 |url-status=live |pages=334–336}}</ref> Nonetheless, they later [[2003 Invasion of Iraq|invaded the country]] with allies, citing "[[Saddam–al-Qaeda conspiracy theory|Saddam Hussein's support for terrorism]]".<ref>{{cite web|url=https://georgewbush-whitehouse.archives.gov/news/releases/2003/03/20030322.html|title=President Discusses Beginning of Operation Iraqi Freedom|access-date=October 29, 2011|archive-date=October 31, 2011|archive-url=https://web.archive.org/web/20111031010540/http://georgewbush-whitehouse.archives.gov/news/releases/2003/03/20030322.html|url-status=live}}</ref> At the time, as many as seven in ten Americans believed the Iraqi president played a role in the 9/11 attacks.<ref>{{cite news |title=US public thinks Saddam had role in 9/11 |website=[[The Guardian]] |url=https://www.theguardian.com/world/2003/sep/07/usa.theobserver |date=September 7, 2003 |access-date=March 20, 2017 |archive-date=March 21, 2017 |archive-url=https://web.archive.org/web/20170321084658/https://www.theguardian.com/world/2003/sep/07/usa.theobserver |url-status=live }}</ref> Three years later, Bush conceded that he had not.<ref>{{cite news |title=Bush: Saddam was not responsible for 9/11 |website=[[The Guardian]] |url=https://www.theguardian.com/world/2006/sep/12/september11.usa2 |date=September 12, 2006 |access-date=March 20, 2017 |archive-date=March 21, 2017 |archive-url=https://web.archive.org/web/20170321085103/https://www.theguardian.com/world/2006/sep/12/september11.usa2 |url-status=live }}</ref>

The [[NATO]] council declared that the terrorist attacks on the United States were an attack on all NATO nations that satisfied [[North Atlantic Treaty#Article 5|Article 5]] of the NATO charter. This marked the first invocation of Article 5, which had been written during the [[Cold War]] with an attack by the Soviet Union in mind.<ref>{{cite web |title=Statement by the North Atlantic Council |publisher=NATO |date=September 15, 2001 |url=http://www.nato.int/docu/pr/2001/p01-124e.htm |access-date=September 4, 2011 |quote=Article 5: The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in the exercise of the right of individual or collective self-defence recognised by Article 51 of the Charter of the United Nations, will assist the Party or Parties so attacked by taking forthwith, individually and in concert with the other Parties, such action as it deems necessary, including the use of armed force, to restore and maintain the security of the North Atlantic area. Any such armed attack and all measures taken as a result thereof shall immediately be reported to the Security Council. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security. |archive-date=December 25, 2018 |archive-url=https://web.archive.org/web/20181225172232/https://www.nato.int/docu/pr/2001/p01-124e.htm%20 |url-status=live }}</ref> Australian Prime Minister [[John Howard]], who was in Washington, D.C., during the attacks, invoked Article IV of the [[ANZUS]] treaty.<ref>{{cite news |title=ABC Conversations with Richard Fidler John Howard Interview Transcript |publisher=Australian Broadcasting Corporation |date=September 2011 |url=http://www.abc.net.au/reslib/201109/r826557_7555516.pdf |access-date=January 25, 2013 |archive-date=May 10, 2013 |archive-url=https://web.archive.org/web/20130510233640/http://www.abc.net.au/reslib/201109/r826557_7555516.pdf |url-status=live }}</ref> The Bush administration announced a [[war on terror]], with the stated goals of bringing bin Laden and Al-Qaeda to justice and preventing the emergence of other terrorist networks.<ref>{{Cite news|url=https://www.washingtonpost.com/wp-srv/nation/specials/attacked/transcripts/bushaddress_092001.html|title=Text: President Bush Addresses the Nation|date=September 20, 2001|access-date=July 4, 2015|newspaper=The Washington Post|last=Bush|first=George|archive-date=August 13, 2021|archive-url=https://web.archive.org/web/20210813093643/https://www.washingtonpost.com/wp-srv/nation/specials/attacked/transcripts/bushaddress_092001.html|url-status=live}}</ref> These goals would be accomplished by imposing economic and military sanctions against states harbouring terrorists, and increasing global surveillance and intelligence sharing.<ref>{{cite web|url=https://www.cia.gov/news-information/cia-the-war-on-terrorism/Counter_Terrorism_Strategy.pdf|title=National Strategy for Combating Terrorism|date=February 2003|access-date=July 4, 2015|publisher=Central Intelligence Agency|archive-date=February 24, 2015|archive-url=https://web.archive.org/web/20150224121111/https://www.cia.gov/news-information/cia-the-war-on-terrorism/Counter_Terrorism_Strategy.pdf|url-status=dead}}</ref>

On September 14, 2001, the [[United States Congress|U.S. Congress]] passed the [[Authorization for Use of Military Force of 2001|Authorization for the use of Military Force Against Terrorists]], which grants the President the authority to use all "necessary and appropriate force" against those whom he determined "planned, authorized, committed or aided" the September 11 attacks or who harboured said persons or groups. It is still in effect.<ref>{{cite web |title=Public Law 107–40—Sept. 18, 2001: Joint Resolution To authorize the use of United States Armed Forces against those responsible for the recent attacks launched against the United States |url=http://www.gpo.gov/fdsys/pkg/PLAW-107publ40/pdf/PLAW-107publ40.pdf |date=September 18, 2001 |access-date=July 4, 2015 |publisher=107th Congress |archive-date=December 7, 2018 |archive-url=https://web.archive.org/web/20181207022906/https://www.gpo.gov/fdsys/pkg/PLAW-107publ40/pdf/PLAW-107publ40.pdf |url-status=live }}</ref>

On October 7, 2001, the [[War in Afghanistan (2001–2021)|War in Afghanistan]] began when U.S. and British forces initiated aerial bombing campaigns targeting [[Taliban]] and Al-Qaeda camps, then later invaded Afghanistan with ground troops of the [[Special Forces]].{{citation needed|date=November 2022}} This eventually led to the overthrow of the Taliban's rule of Afghanistan with the [[Fall of Kandahar]] on December 7, 2001, by U.S.-led [[International Security Assistance Force|coalition forces]].<ref>{{cite web|title=U.S. Military Operations in the Global War on Terrorism: Afghanistan, Africa, the Philippines, and Colombia|url=http://www.au.af.mil/au/awc/awcgate/crs/rl32758.pdf|access-date=July 5, 2015|publisher=[[Air University (United States Air Force)]]|archive-date=September 23, 2015|archive-url=https://web.archive.org/web/20150923181625/http://www.au.af.mil/au/awc/awcgate/crs/rl32758.pdf|url-status=dead}}</ref>

Al-Qaeda leader Osama bin Laden, who went into hiding in the [[Spin Ghar|White Mountains]], was targeted by U.S. coalition forces in the [[Battle of Tora Bora]],<ref name="BBC News 2011-07-11">{{cite news |last=Corera |first=Gordon |date=July 21, 2011 |title=Bin Laden's Tora Bora escape, just months after 9/11 |publisher=BBC News |url=https://www.bbc.co.uk/news/world-us-canada-14190032 |access-date=December 7, 2023 |archive-date=November 29, 2022 |archive-url=https://web.archive.org/web/20221129165659/https://www.bbc.co.uk/news/world-us-canada-14190032 |url-status=live }}</ref> but he escaped across the [[Durand Line|Pakistani border]] and remained out of sight for almost ten years.<ref name="BBC News 2011-07-11" /> In an interview with [[Tayseer Allouni]] on October 21, 2001, Bin Laden stated: <blockquote>The events proved the extent of [[terrorism]] that America exercises in the world. [[George W. Bush|Bush]] stated that the world has to be divided in two: Bush and his supporters, and any country that doesn't get into the global crusade is with the terrorists. What terrorism is clearer than this? Many governments were forced to support this "new terrorism.".. America wouldn't live in security until we live it truly in [[Palestine (region)|Palestine]]. This showed the reality of America, which puts Israel's interest above its own people's interest. America won't get out of this crisis until it gets out of the [[Arabian Peninsula]], and until it stops its [[Israel–United States military relations|support of Israel]].<ref>{{cite book|title=Al Qaeda Now|year=2005|publisher=Cambridge University Press|isbn=978-0-521-85911-0|first1=Karen|last1=J. Greenberg|pages=192–206|chapter=October 21, 2001 – Interview with Tayseer Alouni |location= New York, US}}</ref></blockquote>

== Aftermath ==
{{Main|Aftermath of the September 11 attacks}}

{{See also|Post-9/11}}

=== Health issues ===
{{Main|Health effects arising from the September 11 attacks}}

[[File:Dust covered 911 victims.jpg|thumb|Survivors covered in dust after the collapse of the [[World Trade Center (1973–2001)|World Trade towers]]; a photograph of another dust-covered victim, [[Marcy Borders]], subsequently gained much attention.<ref>{{Cite web |date=September 11, 2021 |title=The tragic story of 'Dust Lady' and other 9/11 survivors with fatal health problems |url=https://www.independent.co.uk/news/world/americas/marcy-borders-dust-lady-911-b1916365.html |access-date=September 27, 2023 |website=The Independent |language=en}}</ref><ref>{{Cite news |last=Pilkington |first=Ed |date=September 21, 2015 |title=9/11 'Dust Lady' Marcy Borders: depression, rehab, back from the brink – then a final bombshell |language=en-GB |work=The Guardian |url=https://www.theguardian.com/us-news/2015/sep/21/911-dust-lady-marcy-borders-depression-rehab-back-from-the-brink-then-a-final-bombshell |access-date=September 27, 2023 |issn=0261-3077}}</ref>]]
Hundreds of thousands of tons of toxic debris containing more than 2,500 contaminants and known carcinogens were spread across Lower Manhattan when the towers collapsed.<ref>{{cite news |last=Gates |first=Anita |title=Buildings Rise from Rubble while Health Crumbles |url=https://www.nytimes.com/2006/09/11/arts/television/11dust.html |work=The New York Times |date=September 11, 2006 |access-date=September 4, 2011}}</ref><ref>{{cite news|url=https://www.nytimes.com/imagepages/2006/09/05/nyregion/20060905_HEALTH_GRAPHIC.html |title=What was Found in the Dust |work=The New York Times |date=September 5, 2006|access-date=September 4, 2011}}</ref> Exposure to the toxins in the debris is alleged to have contributed to [[Health effects arising from the September 11 attacks|fatal or debilitating illnesses]] among people who were at Ground Zero.<ref name="CNN 2007-05-24">{{cite news|title=New York: 9/11 toxins caused death|publisher=CNN|date=May 24, 2007|url=http://www.cnn.com/2007/US/05/24/wtc.dust/index.html|access-date=September 4, 2011 |archive-url=https://web.archive.org/web/20070618154824/http://www.cnn.com/2007/US/05/24/wtc.dust/index.html |archive-date=June 18, 2007}}</ref><ref>{{cite news |url=https://www.nytimes.com/2006/05/13/nyregion/13symptoms.html |title=Tracing Lung Ailments That Rose With 9/11 Dust |last=DePalma |first=Anthony |date=May 13, 2006|work=The New York Times |access-date=September 4, 2011}}</ref> The Bush administration ordered the [[Environmental Protection Agency]] (EPA) to issue reassuring statements regarding air quality in the aftermath of the attacks, citing national security, but the EPA did not determine that air quality had returned to pre-September 11 levels until June 2002.<ref>{{cite news|last=Heilprin |first=John |title=White House edited EPA's 9/11 reports |work=Seattle Post-Intelligencer |date=June 23, 2003 |url=http://www.seattlepi.com/default/article/White-House-edited-EPA-s-9-11-reports-1122465.php |access-date=September 4, 2011}}</ref>

Health effects extended to residents, students, and office workers of Lower Manhattan and nearby [[Chinatown, Manhattan|Chinatown]].<ref>{{cite web |title=Updated Ground Zero Report Examines Failure of Government to Protect Citizens |publisher=Sierra Club |year=2006 |url=http://www.sierraclub.org/groundzero/ |archive-url=https://web.archive.org/web/20100611191219/http://www.sierraclub.org/groundzero/ |archive-date=June 11, 2010 |access-date=September 4, 2011}}</ref> Several deaths have been linked to the toxic dust, and victims' names were included in the World Trade Center memorial.<ref>{{cite news |last=Smith |first=Stephen |title=9/11 "Wall of Heroes" To Include Sick Cops |url=https://www.cbsnews.com/news/9-11-wall-of-heroes-to-include-sick-cops/ |publisher=CBS News |date=April 28, 2008 |access-date=September 4, 2011}}</ref> An estimated 18,000 people have developed illnesses as a result of the toxic dust.<ref>{{cite news |last=Shukman |first=David |title=Toxic dust legacy of 9/11 plagues thousands of people |url=https://www.bbc.co.uk/news/world-us-canada-14738140 |publisher=BBC News |date=September 1, 2011|access-date=September 11, 2011}}</ref> There is also scientific speculation that exposure to toxic products in the air may have negative effects on fetal development.{{Citation needed|date=September 2023}} A study of rescue workers released in April 2010 found that all those studied had impaired lung function.<ref>{{cite news|last=Grady|first=Denise|title=Lung Function of 9/11 Rescuers Fell, Study Finds|url=https://www.nytimes.com/2010/04/08/nyregion/08lung.html|access-date=September 4, 2011|newspaper=The New York Times|date=April 7, 2010}}</ref>

Years after the attacks, legal disputes over the costs of related illnesses were still in the court system. On October 17, 2006, a federal judge rejected New York City's refusal to pay for health costs for rescue workers, allowing for the possibility of suits against the city.<ref>{{cite news |first=Anthony |last=DePalma |title=Many Ground Zero Workers Gain Chance at Lawsuits |work=The New York Times |date=October 18, 2006 |url=https://www.nytimes.com/2006/10/18/nyregion/nyregionspecial3/18toxic.html |access-date=September 4, 2011}}</ref> Government officials have been faulted for urging the public to return to lower Manhattan in the weeks shortly after the attacks. Christine Todd Whitman, administrator of the EPA in the attacks' aftermath, was heavily criticized by a U.S. District Judge for incorrectly saying that the area was environmentally safe.<ref>{{cite news|first=Larry |last=Neumeister |url=http://www.sfgate.com/cgi-bin/article.cgi?file=/n/a/2006/02/02/national/a142556S81.DTL |title=Judge Slams Ex-EPA Chief Over Sept. 11 |agency=Associated Press |work=San Francisco Chronicle |date=February 2, 2006 |access-date=September 4, 2011 |archive-url=https://web.archive.org/web/20080524084609/http://www.sfgate.com/cgi-bin/article.cgi?file=%2Fn%2Fa%2F2006%2F02%2F02%2Fnational%2Fa142556S81.DTL |archive-date=May 24, 2008 |url-status=dead }}</ref> Mayor Giuliani was criticized for urging financial industry personnel to return quickly to the greater [[Wall Street]] area.<ref>{{cite news |last=Smith |first=Ben |title=Rudy's black cloud. WTC health risks may hurt Prez bid |url=http://www.nydailynews.com/archives/news/rudy-black-cloud-wtc-health-risks-hurt-prez-bid-article-1.618126 |work=New York Daily News |date=September 18, 2006 |access-date=May 29, 2014}}</ref>

The [[James L. Zadroga 9/11 Health and Compensation Act]] (2010) allocated $4.2{{spaces}}billion to create the [[World Trade Center Health Program]], which provides testing and treatment for people with long-term health problems related to the 9/11 attacks.<ref>{{cite news|url=https://www.cnn.com/2010/POLITICS/12/20/new.york.9.11.bill/index.html |publisher=[[CNN]] |title=Bloomberg urges passage of 9/11 health bill |date=December 20, 2010}}</ref><ref name="WTCHP faq">{{cite web|title=World Trade Center Health Program FAQ|url=https://www.cdc.gov/wtc/faq.html|publisher=Centers for Disease Control and Prevention|access-date=July 2, 2012}}</ref> The WTC Health Program replaced preexisting 9/11-related health programs such as the Medical Monitoring and Treatment Program and the WTC Environmental Health Center program.<ref name="WTCHP faq" />

In 2020, the NYPD confirmed that 247 NYPD police officers had died due to 9/11-related illnesses. In September 2022, the FDNY confirmed that 299 firefighters had died due to 9/11-related illnesses. Both agencies believe that the death toll will rise dramatically in the coming years. The [[Port Authority of New York and New Jersey Police Department]] (PAPD), the law enforcement agency with jurisdiction over the World Trade Center, confirmed that four of its police officers have died of 9/11-related illnesses. The chief of the PAPD at the time, Joseph Morris, made sure that industrial-grade respirators were provided to all PAPD police officers within 48 hours and decided that the same 30 to 40 police officers would be stationed at the World Trade Center pile, drastically lowering the number of total PAPD personnel who would be exposed to the air. The FDNY and NYPD had rotated hundreds, if not thousands, of different personnel from all over New York City to the pile without adequate respirators and breathing equipment that could have prevented future diseases.<ref>{{cite web |url=https://www1.nyc.gov/site/nypd/about/memorials/9-11-tribute.page |title=9/11 Tribute |publisher=NYPD |access-date=September 19, 2022}}{{title missing|date=September 2022}}</ref><ref>{{cite web |url=https://www1.nyc.gov/site/fdny/news/022-22/fdny-adds-37-names-memorial-wall-deaths-related-world-trade-center-illnesses |title=FDNY Adds 37 Names to Memorial Wall for Deaths Related to World Trade Center Illnesses|website=www1.nyc.gov |date=September 13, 2022|access-date=September 19, 2022}}{{title missing|date=September 2022}}</ref><ref>{{cite news |url=https://www.thechiefleader.com/stories/port-authority-police-union-leader-still-pain-for-families-of-911-cops-free-article,6828 |title=Port Authority Police-Union Leader: Still Pain for Families of 9/11 Cops (Free Article)|website=The Chief Leader |access-date=September 19, 2022}}{{title missing|date=September 2022}}</ref><ref>{{cite news |url=https://www.nydailynews.com/new-york/september-11/ny-9-11-port-authority-police-saved-lives-20210906-gtmdsurzt5fjxaqhp6bdiq3x3q-story.html |title=Swift action on 9/11 by NYC's Port Authority police saved lives|website=New York Daily News |access-date=September 19, 2022}}{{title missing|date=September 2022}}</ref>

=== Economic ===
{{Main|Economic effects of the September 11 attacks}}

[[File:Deficits vs. Debt Increases - 2008.png|thumb|[[United States federal budget|U.S. deficit]] and [[United States public debt|debt]] increases in the seven years following the attacks from 2001 to 2008.]]
The attacks had a significant economic impact on the US and world markets.<ref>{{cite web |last=Makinen|first=Gail |url=https://fas.org/irp/crs/RL31617.pdf |title=The Economic Effects of 9/11: A Retrospective Assessment |page=17 |date=September 27, 2002 |publisher=Congressional Research Service, [[Library of Congress]] |access-date=September 4, 2011 }}</ref> The stock exchanges did not open on September 11 and remained closed until September 17. Reopening, the [[Dow Jones Industrial Average]] (DJIA) fell 684 points, or 7.1%, to 8921, a record-setting one-day point decline.<ref>{{cite news |title=Markets reopen, plunge |last=Barnhart |first=Bill |url=http://www.chicagotribune.com/business/chi-010917markets,0,5287650.story|work=Chicago Tribune |date=September 17, 2001 |access-date=April 11, 2012}}</ref> By the end of the week, the DJIA had fallen 1,369.7 points (14.3%), at the time its largest one-week point drop in history. In 2001 dollars, U.S. stocks lost $1.4{{spaces}}trillion in valuation for the week.<ref name="MarkDec">{{cite news|last=Fernandez |first=Bob |title=U.S. Markets Decline Again |work=KRTBN Knight Ridder Tribune Business News |date=September 22, 2001}}</ref>

In New York City, about 430,000 job months and $2.8{{spaces}}billion in wages were lost in the first three months after the attacks. The economic effects were mainly on the economy's export sectors.<ref>{{cite journal |last1=Dolfman |first1=Michael L. |last2=Wasser |first2=Solidelle F. |journal=Monthly Labor Review |volume=127 |year=2004 |title=9/11 and the New York City Economy}}</ref><ref name="IAGS cost">{{cite web |title=How much did the September 11 terrorist attack cost America? |url=http://www.iags.org/costof911.html |access-date=April 30, 2014 |publisher=Institute for the Analysis of Global Security}}</ref><ref name="PEARL9/11">{{cite book |last=Morgan |first=Matthew J. |url=https://books.google.com/books?id=JDEfUCll7DcC |title=The Impact of 9/11 on Politics and War: The Day that Changed Everything? |date=August 4, 2009 |publisher=Palgrave Macmillan |isbn=978-0-230-60763-7 |page=222}}</ref> The city's GDP was estimated to have declined by $27.3{{spaces}}billion for the last three months of 2001 and all of 2002. The U.S. government provided $11.2{{spaces}}billion in immediate assistance to the [[Government of New York City]] in September 2001, and $10.5{{spaces}}billion in early 2002 for economic development and infrastructure needs.<ref name="crs-5">{{cite web|last=Makinen|first=Gail |url=https://fas.org/irp/crs/RL31617.pdf |title=The Economic Effects of 9/11: A Retrospective Assessment |page=5 |date=September 27, 2002 |publisher=Congressional Research Service, [[Library of Congress]] |access-date=September 4, 2011 }}</ref>

Also hurt were small businesses in [[Lower Manhattan]] near the World Trade Center (18,000 of which were destroyed or displaced), resulting in lost jobs and wages. Assistance was provided by [[Small Business Administration]] loans; federal government Community Development Block Grants; and Economic Injury Disaster Loans.<ref name="crs-5" /> Some {{convert|31900000|sqft|m2}} of Lower Manhattan office space was damaged or destroyed.<ref>{{cite web |last=Hensell |first=Lesley |title=Tough Times Loom For Manhattan Commercial Market |url=http://realtytimes.com/rtpages/20011214_downtown.htm |website=Realty Times |date=December 14, 2001 |access-date=September 4, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110814003420/http://realtytimes.com/rtpages/20011214_downtown.htm |archive-date=August 14, 2011 }}</ref> Many wondered whether these jobs would return, and if the damaged tax base would recover.<ref>{{cite web |last=Parrott |first=James |title=The Employment Impact of the September 11 World Trade Center Attacks: Updated Estimates based on the Benchmarked Employment Data |publisher=The Fiscal Policy Institute |date=March 8, 2002 |url=http://www.fiscalpolicy.org/Employment%20Impact%20of%20September%2011_Update.pdf |access-date=September 4, 2011 |archive-date=September 11, 2011 |archive-url=https://web.archive.org/web/20110911170813/http://www.fiscalpolicy.org/Employment%20Impact%20of%20September%2011_Update.pdf |url-status=dead }}</ref> Studies of 9/11's economic effects show the Manhattan office real-estate market and office employment were less affected than first feared, because of the financial services industry's need for face-to-face interaction.<ref>{{cite SSRN |last=Fuerst |first=Franz |title=Exogenous Shocks and Real Estate Rental Markets: An Event Study of the 9/11 Attacks and their Impact on the New York Office Market|date=September 7, 2005 |ssrn=800006}}</ref><ref>{{cite magazine|last=Russell |first=James S. |title=Do skyscrapers still make sense? Revived downtowns and new business models spur tall-building innovation |magazine=Architectural Record |date=November 7, 2004 |url=http://archrecord.construction.com/innovation/2_Features/0411SkyscraperSense.asp |access-date=September 4, 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110808062854/http://archrecord.construction.com/innovation/2_Features/0411SkyscraperSense.asp |archive-date=August 8, 2011}}</ref>

North American air space was closed for several days after the attacks and air travel decreased upon its reopening, leading to a nearly 20% cutback in air travel capacity, and exacerbating financial problems in the struggling [[Airline|U.S. airline industry]].<ref>{{cite web |last1=Bhadra |first1=Dipasis |last2=Texter |first2=Pamela |title=Airline Networks: An Econometric Framework to Analyze Domestic U.S. Air Travel |publisher=[[United States Department of Transportation]] |year=2004 |url=http://www.bts.gov/publications/journal_of_transportation_and_statistics/volume_07_number_01/html/paper_06/ |access-date=September 4, 2011 |archive-url=https://web.archive.org/web/20050330035744/http://www.bts.gov/publications/journal_of_transportation_and_statistics/volume_07_number_01/html/paper_06/ |archive-date=March 30, 2005 |url-status=dead}}</ref>

The September 11 attacks also led to the U.S. [[War in Afghanistan (2001–present)|wars in Afghanistan]] and [[Iraq War|Iraq]],<ref>{{cite news|url=https://www.washingtonpost.com/blogs/ezra-klein/post/bin-ladens-war-against-the-us-economy/2011/04/27/AFDOPjfF_blog.html |title=Bin Laden's war against the U.S. economy |newspaper=The Washington Post |date=May 3, 2011 |first=Thomas |last=Heath}}</ref> as well as additional [[homeland security]] spending, totaling at least $5{{spaces}}trillion.<ref>{{cite news|url=https://www.washingtonpost.com/business/economy/osama-bin-laden-didnt-win-but-he-was-enormously-successful/2011/05/02/AFexZjbF_story.html |title=Osama bin Laden didn't win, but he was 'enormously successful' |newspaper=The Washington Post |first=Suzy |last=Khimm |date=May 3, 2011}}</ref>

=== Effects in Afghanistan ===
{{further|War in Afghanistan (2001–2021)|Aftermath of the War in Afghanistan (2001–2021)|Killing of Ayman al-Zawahiri}}
{{Quote box
| width = 23em
| align = right
| quote = If Americans are clamouring to bomb Afghanistan back to the [[Stone Age]], they ought to know that this nation does not have so far to go. This is a post-apocalyptic place of felled cities, parched land and downtrodden people.
| source = — [[Barry Bearak]], ''[[The New York Times]]'', September 13, 2001<ref name="TalibanPlead" />
}}
Most of the [[Afghans|Afghan population]] was already going hungry at the time of the September 11 attacks.<ref>{{Cite news|url=https://www.economist.com/unknown/2001/09/26/horror-in-afghanistan|title=Horror in Afghanistan|date=September 26, 2001|newspaper=The Economist}}</ref> In the aftermath of the attacks, tens of thousands of people attempted to flee Afghanistan due to the possibility of military retaliation by the US. Pakistan, already [[Afghans in Pakistan|home to many Afghan refugees]] from previous conflicts, closed its border with Afghanistan on September 17, 2001.<ref name="speechto" /> Thousands of Afghans also fled to the frontier with [[Tajikistan]] but were denied entry.<ref>{{Cite web|url=https://reliefweb.int/report/afghanistan/tajikistan-holed-border|title=Tajikistan: Holed up at the border – Afghanistan|website=ReliefWeb|date=September 28, 2001 }}</ref> The [[Taliban]] leaders in Afghanistan pleaded against military action, saying "We appeal to the United States not to put Afghanistan into more misery because our people have suffered so much", referring to [[Afghanistan conflict (1978-present)|two decades of conflict]] and the humanitarian crisis attached to it.<ref name="TalibanPlead">{{Cite news|url=https://www.nytimes.com/2001/09/13/us/after-attacks-afghans-taliban-plead-for-mercy-miserable-land-nothing.html|title=After The Attacks: The Afghans; Taliban Plead for Mercy to the Miserable in a Land of Nothing|first=Barry|last=Bearak|newspaper=The New York Times|date=September 13, 2001}}</ref>

All United Nations expatriates had left Afghanistan after the attacks and no national or international aid workers were at their post. Workers were instead preparing in bordering countries like Pakistan, China and Uzbekistan to prevent a potential "humanitarian catastrophe", amid a critically low food stock for the Afghan population.<ref>{{cite news|url=https://edition.cnn.com/2001/WORLD/asiapcf/central/09/20/ret.afghan.refugees/|title=CNN – Afghan refugee crisis spreads – September 20, 2001|publisher=CNN}}</ref> The [[World Food Programme]] stopped importing wheat to Afghanistan on September 12 due to security risks.<ref>{{Cite news|url=http://news.bbc.co.uk/2/hi/south_asia/1556117.stm|title=Aid shortage adds to Afghan woes|date=September 22, 2001|via=BBC News}}</ref>

{{multiple image
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| image2            = Last American Soldier leaves Afghanistan.jpg
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| footer            = ''From left to right'': U.S. soldiers engaged in the war on terror in Afghanistan in May 2006. • Army Major General [[Chris Donahue (general)|Chris Donahue]] left Afghanistan as the final American soldier on August 30, 2021.
| caption1          = 
}}

Approximately one month after the attacks, the United States led a broad [[Participants in Operation Enduring Freedom|coalition of international forces]] to overthrow the Taliban regime from Afghanistan for their harboring of Al-Qaeda.<ref name="speechto">{{cite news|title=U.S. President Bush's speech to United Nations |publisher=CNN|date=November 10, 2001 |url=http://archives.cnn.com/2001/US/11/10/ret.bush.un.transcript/index.html |url-status=dead |archive-url=https://web.archive.org/web/20060615023853/http://archives.cnn.com/2001/US/11/10/ret.bush.un.transcript/index.html |archive-date=June 15, 2006 |access-date=May 29, 2014}}</ref> Though Pakistani authorities were initially reluctant to align themselves with the US against the Taliban, they permitted the coalition access to their military bases, and arrested and handed over to the U.S. over 600 suspected Al-Qaeda members.<ref>{{cite news|title=Musharraf 'bullied' into supporting US war on terror|url=http://zeenews.india.com/news/south-asia/musharraf-bullied-into-supporting-us-war-on-terror-ex-general_586640.html|access-date=September 4, 2011|publisher=Zee News|date=December 11, 2009}}</ref><ref>{{cite news |last=Khan |first=Aamer Ahmed |title=Pakistan and the 'key al-Qaeda' man |url=http://news.bbc.co.uk/2/hi/south_asia/4513281.stm |publisher=BBC News |date=May 4, 2005 |access-date=September 4, 2011}}</ref>

In 2011, the U.S. and NATO under [[Presidency of Barack Obama|President Obama]] initiated a [[Withdrawal of United States troops from Afghanistan (2011–2016)|drawdown of troops]] in Afghanistan finalized in 2016. During the presidencies of [[Donald Trump]] and [[Joe Biden]] in 2020 and 2021, the United States alongside its NATO allies [[Withdrawal of United States troops from Afghanistan (2020–2021)|withdrew all troops from Afghanistan]] completing the withdrawal of all regular U.S. troops on August 30, 2021.<ref name="DOD Cronk Biden Announces">{{Cite web |last=Cronk |first=Terri Moon |date=April 14, 2021 |title=Biden Announces Full U.S. Troop Withdrawal From Afghanistan by Sept. 11 |url=https://www.defense.gov/Explore/News/Article/Article/2573268/biden-announces-full-us-troop-withdrawal-from-afghanistan-by-sept-11/ |access-date=August 16, 2021 |publisher=U.S. Department of Defense |language=en-US}}</ref><ref name="White House 2021-04-14">{{Cite web |date=April 14, 2021 |title=Remarks by President Biden on the Way Forward in Afghanistan |url=https://www.whitehouse.gov/briefing-room/speeches-remarks/2021/04/14/remarks-by-president-biden-on-the-way-forward-in-afghanistan/ |access-date=August 16, 2021 |website=The White House |language=en-US}}</ref><ref name="Time 2021">{{cite magazine |last=Satia |first=Priya |date=April 27, 2021 |editor-last=Felsenthal |editor-first=Edward |editor-link=Edward Felsenthal |title=History's Warning for the U.S. Withdrawal From Afghanistan |url=https://time.com/5959073/afghanistan-withdrawal-empire-history/ |url-status=live |magazine=[[Time (magazine)|Time]] |location=New York City |archive-url=https://web.archive.org/web/20210427194916/https://time.com/5959073/afghanistan-withdrawal-empire-history/ |archive-date=April 27, 2021 |access-date=April 27, 2021}}</ref> The withdrawal marked the end of the [[War in Afghanistan (2001–2021)|2001–2021 War in Afghanistan]]. Biden said that after nearly 20 years of war, it was clear that the U.S. military could not transform Afghanistan into a modern democracy.<ref>{{Cite news |last1=Zucchino |first1=David |date=October 7, 2021 |title=The U.S. War in Afghanistan: How It Started, and How It Ended |newspaper=The New York Times |url=https://www.nytimes.com/article/afghanistan-war-us.html}}</ref>

=== Cultural influence ===
{{Main|Cultural influence of the September 11 attacks}}
{{Further|List of cultural references to the September 11 attacks|Entertainment affected by the September 11 attacks|Osama bin Laden in popular culture}}
{{See also|Osama bin Laden (elephant)}}
Immediate responses to 9/11 included greater focus on home life and time spent with family, higher church attendance, and increased expressions of patriotism such as the flying of American flags.<ref name="Carducci2009b">{{cite book|first=Bernardo J.|last=Carducci|title=The Psychology of Personality: Viewpoints, Research, and Applications|url=https://books.google.com/books?id=1gJPXv5wQbIC&pg=PA200|access-date=January 16, 2012 |date=February 20, 2009|publisher=Wiley-Blackwell|isbn=978-1-4051-3635-8|pages=200–}}</ref> [[Clear Channel memorandum|The radio industry responded by removing certain songs from playlists]], and the attacks have subsequently been used as background, narrative, or thematic elements in [[List of films about the September 11 attacks|film]], [[List of songs about the September 11 attacks|music]], [[List of books about the September 11 attacks|literature]], and [[Humor based on the September 11 attacks|humour]]. Already-running television shows as well as programs developed after 9/11 have reflected [[post-9/11]] cultural concerns.<ref name="Pop Culture Guide">{{cite book |last1=Quay |first1=Sara |last2=Damico |first2=Amy |title=September 11 in Popular Culture: A Guide |publisher=[[Greenwood Publishing Group]] |date=September 14, 2010 |isbn=978-0-313-35505-9|url=https://books.google.com/books?id=lx7i4YHl_NoC}}</ref>

<!-- "STOP. Before expanding or removing 9/11 conspiracy theories, please note that the verbiage being used was arrived at after months of discussion and consensus-building. If you think something should be changed, please start a discussion on the article talk page. Thank you." -->[[9/11 conspiracy theories]] have become a social phenomenon, despite a lack of support from expert scientists, engineers, and historians.<ref>{{cite news |title=9/11 conspiracy theories won't stop|first=Joshua|last=Norman|date=September 11, 2011|publisher=CBS News|url=https://www.cbsnews.com/news/9-11-conspiracy-theories-wont-stop/}}</ref> 9/11 has also had a major impact on the religious faith of many individuals; for some it strengthened, to find [[consolation]] to cope with the loss of loved ones and overcome their grief; others started to question their faith or lose it entirely because they [[Problem of evil|could not reconcile it]] with their view of religion.<ref>{{cite news |url=http://www.huffingtonpost.com/2011/08/29/september-11-challenged-faith_n_941017.html|title=After 9/11, Some Run Toward Faith, Some Run The Other Way|work=HuffPost|date=August 29, 2011|access-date=April 6, 2013}}</ref><ref>{{cite news |url=https://www.pbs.org/wgbh/pages/frontline/shows/faith/questions/god.html|title=Faith and Doubt at Ground Zero – The Question of God|work=PBS Frontline|access-date=April 6, 2013}}</ref>

The culture of America, after the attacks, is noted for heightened security and an increased demand thereof, as well as [[paranoia]] and [[anxiety]] regarding future terrorist attacks against most of the nation. Psychologists have also confirmed that there has been an increased amount of national anxiety in commercial air travel.<ref>{{cite web |url=http://www.psychologytoday.com/articles/200201/anxiety-after-911 |title=Anxiety After 9/11 |first1=Brad |last1=Schmidt |first2=Jeffrey |last2=Winters |work=[[Psychology Today]] |date=January 1, 2002 |access-date=October 11, 2013}}</ref> Anti-Muslim hate crimes rose nearly ten-fold in 2001 and have subsequently remained "roughly five times higher than the pre-9/11 rate".<ref>{{cite news |last1=Ingraham |first1=Christopher |title=Anti-Muslim hate crimes are still five times more common today than before 9/11 |url=https://www.washingtonpost.com/news/wonk/wp/2015/02/11/anti-muslim-hate-crimes-are-still-five-times-more-common-today-than-before-911/ |access-date=December 20, 2023 |newspaper=[[The Washington Post]] |url-access=limited |date=February 11, 2015}}</ref>

=== Government policies towards terrorism ===
{{Further|War on terror|Anti-terrorism legislation|Airport security repercussions due to the September 11 attacks|Legal issues related to the September 11 attacks}}
{{See also|Senate Intelligence Committee report on CIA torture}}
[[File:CIA illegal flights.svg|upright=1.35|thumb|Alleged "[[extraordinary rendition]]" illegal flights of the [[Central Intelligence Agency|CIA]], as reported by Polish newspaper ''[[Rzeczpospolita (newspaper)|Rzeczpospolita]]''<ref>{{cite web |url=http://www.rp.pl/artykul/292283.html |title=Politycy nie pozwolili śledczym tropić lotów CIA – Rzeczpospolita |language=pl |work=[[Rzeczpospolita (newspaper)|Rzeczpospolita]] |date=April 17, 2009 |access-date=February 24, 2022 |archive-date=July 11, 2015 |archive-url=https://web.archive.org/web/20150711125637/http://www.rp.pl/artykul/292283.html |url-status=dead }}</ref>]]
As a result of the attacks, many governments across the world passed legislation to combat terrorism.<ref>{{cite journal |title=Terrorism in the Asia-Pacific: Threat and Response |journal=[[The Journal of Asian Studies]] |year=2004 |first=Andrew |last=Scobell |volume=63 |issue=4 |pages=1078–79 |doi=10.1017/S0021911804002463|s2cid=163030372}}</ref> In Germany, where several of the 9/11 terrorists had resided and taken advantage of that country's liberal asylum policies, two major anti-terrorism packages were enacted. The first removed legal loopholes that permitted terrorists to live and raise money in Germany. The second addressed the effectiveness and communication of intelligence and law enforcement.<ref>{{cite web |url=https://fas.org/irp/crs/RL32710.pdf |title=Germany's Role in Fighting Terrorism: Implications for U.S. Policy |access-date=September 4, 2011 |last1=Miko |first1=Francis |last2=Froehlich |first2=Christian |date=December 27, 2004 |publisher=[[Federation of American Scientists]]}}</ref> Canada passed the [[Canadian Anti-Terrorism Act]], their first anti-terrorism law.<ref>{{cite news|title=Anti-terrorism Act|url=http://www.cbc.ca/news2/background/cdnsecurity/|access-date=November 12, 2013 |publisher=CBC News|date=February 27, 2007}}</ref> The United Kingdom passed the [[Anti-terrorism, Crime and Security Act 2001]] and the [[Prevention of Terrorism Act 2005]].<ref>{{cite news |title=Q and A: Anti-terrorism legislation |date=October 17, 2003 |url=http://news.bbc.co.uk/2/hi/uk_news/3197394.stm |publisher=BBC News |access-date=September 4, 2011}}</ref><ref>{{cite news |first=Sam |last=Coates |title=After all the fuss dies down, what really happened |date=November 10, 2005 |url=http://www.timesonline.co.uk/tol/news/uk/article588553.ece |archive-url=https://web.archive.org/web/20110814133937/http://www.timesonline.co.uk/tol/news/uk/article588553.ece |url-status=dead |archive-date=August 14, 2011 |work=The Times |access-date=September 4, 2011}}</ref> New Zealand enacted the [[Terrorism Suppression Act 2002]].<ref>{{cite web|title=Terrorism Suppression Act 2002|url=http://legislation.co.nz/act/public/2002/0034/19.0/DLM2493700.html|publisher=New Zealand Government|access-date=September 4, 2011|url-status=dead |archive-url=https://web.archive.org/web/20111219044052/http://legislation.co.nz/act/public/2002/0034/19.0/DLM2493700.html|archive-date=December 19, 2011}}</ref>

In the United States, the [[Department of Homeland Security]] was created by the [[Homeland Security Act of 2002]] to coordinate domestic anti-terrorism efforts. The [[USA Patriot Act]] gave the federal government greater powers, including the authority to detain foreign terror suspects for a week without charge; to monitor terror suspects' telephone communications, e-mail, and Internet use; and to prosecute suspected terrorists without time restrictions. The FAA ordered that aeroplane cockpits be reinforced to prevent terrorists from gaining control of planes and assigned [[sky marshals]] to flights.

Further, the [[Aviation and Transportation Security Act]] made the federal government, rather than airports, responsible for [[airport security]]. The law created the [[Transportation Security Administration]] to inspect passengers and luggage, causing long delays and concern over passenger privacy.<ref name="Modern World History">{{cite book |last1=Beck |first1=Roger |title=Modern World History |chapter=20 |publisher=[[Holt McDougal]] |year=2004 |pages=657–658 |isbn=978-0-618-69012-1|chapter-url=https://books.google.com/books?id=WfSPAAAACAAJ}}</ref> After suspected abuses of the USA Patriot Act were [[Global surveillance disclosures (2013–present)|brought to light]] in June 2013 with articles about the collection of American call records by the [[National Security Agency|NSA]] and the [[PRISM (surveillance program)|PRISM]] program, Representative [[Sensenbrenner|Jim Sensenbrenner]] (of [[Wisconsin]]), who introduced the Patriot Act in 2001, said that the NSA overstepped its bounds.<ref>{{cite news|url=https://www.nytimes.com/2013/06/07/opinion/president-obamas-dragnet.html|title=President Obama's Dragnet|newspaper=The New York Times|date=June 6, 2013 }}</ref><ref>{{cite web|url=http://sensenbrenner.house.gov/news/documentsingle.aspx?DocumentID=337001|title=Author of Patriot Act: FBI's FISA Order is Abuse of Patriot Act|date=June 6, 2013|url-status=dead |archive-url=https://web.archive.org/web/20130610061511/http://sensenbrenner.house.gov/news/documentsingle.aspx?DocumentID=337001|archive-date=June 10, 2013}}</ref>

[[Criticism of the war on terror]] has focused on its morality, efficiency, and cost. According to a 2021 report by the [[Costs of War Project]], the several post-9/11 wars participated in by the United States in its [[war on terror]] have caused the displacement, conservatively calculated, of 38 million people in Afghanistan, Pakistan, Iraq, Libya, Syria, Yemen, Somalia, and the Philippines.<ref>{{cite web |first1=David |last1=Vine |first2=Cala |last2=Coffman |first3=Katalina |last3=Khoury |first4=Madison |last4=Lovasz |first5=Helen |last5=Bush |first6=Rachel |last6=Leduc |first7=Jennifer |last7=Walkup |url=https://watson.brown.edu/costsofwar/files/cow/imce/papers/2020/Displacement_Vine%20et%20al_Costs%20of%20War%202020%2009%2008.pdf |title=Creating Refugees: Displacement Caused by the United States' Post-9/11 Wars |publisher=[[Watson Institute for International and Public Affairs]] |date=September 8, 2020}}</ref><ref>{{cite news |first=David |last=Vine |url=https://www.theguardian.com/commentisfree/2020/sep/18/us-wars-iraq-george-w-bush |title=US-led wars have displaced 37&nbsp;m people. America should accept responsibility |work=[[The Guardian]] |date=September 18, 2020}}</ref><ref name="Costs of War">{{Cite web|title=Latest Figures |website=Costs of War|url=https://watson.brown.edu/costsofwar/figures|access-date=September 1, 2021 |language=en}}</ref> They estimated these wars caused the deaths of 897,000 to 929,000 people directly and cost $8&nbsp;trillion.<ref name="Costs of War" /> In a 2023 report, the Costs of War Project estimated that there have been between 3.6 and 3.7&nbsp;million indirect deaths in the post-9/11 war zones, with the total death toll being 4.5 to 4.6&nbsp;million. The report defined post-9/11 war zones as conflicts that included significant United States counter-terrorism operations since 9/11, which in addition to the wars in [[Iraqi conflict|Iraq]], [[War in Afghanistan (2001–2021)|Afghanistan]] and [[Insurgency in Khyber Pakhtunkhwa|Pakistan]], also includes the civil wars in [[Syrian civil war|Syria]], [[Yemeni Civil War (2014–present)|Yemen]], [[Libyan Crisis (2011–present)|Libya]] and [[Somali Civil War|Somalia]].<ref name=":2" /> The report derived its estimate of indirect deaths using a calculation from the [[Geneva Declaration on Armed Violence and Development|Geneva Declaration of Secretariat]] which estimates that for every person directly killed by war, four more die from the indirect consequences of war.<ref name=":2" /> The [[U.S. Constitution]] and [[U.S. law]] prohibits the use of [[Torture in the United States|torture]], yet such [[Human rights violations by the CIA|human rights violations occurred]] during the war on terror under the euphemism "[[Enhanced interrogation techniques|enhanced interrogation]]".<ref>[https://apnews.com/4925f7f0fa654853bd6f2f57174179fe In Yemen's secret prisons, UAE tortures and US interrogates]. Associated Press, 2017.</ref><ref>{{cite news |title=Twenty Years On: The Legacy of 9/11 |url=https://www.hrw.org/news/2021/09/09/twenty-years-legacy-9/11 |publisher=Human Rights Watch |date=September 9, 2021}}</ref> In 2005, ''The Washington Post'' and [[Human Rights Watch]] (HRW) published revelations concerning CIA flights and "[[CIA black sites|black sites]]", covert prisons operated by the [[Central Intelligence Agency|CIA]].<ref>{{cite news |title=Europeans Probe Secret CIA Flights |url=https://www.washingtonpost.com/wp-dyn/content/article/2005/11/16/AR2005111602198.html |newspaper=The Washington Post |first=Craig |last=Whitlock |date=November 17, 2005}}</ref><ref>{{cite news |title=EU to look into 'secret US jails' |url=http://news.bbc.co.uk/2/hi/europe/4403166.stm |publisher=BBC News |date=November 3, 2005}}</ref> The term "torture by proxy" is used by some critics to describe situations in which the CIA and other U.S. agencies have [[Extraordinary rendition|transferred suspected terrorists]] to countries known to employ torture.<ref>"[https://www.huffingtonpost.com/2009/08/28/new-cia-docs-detail-bruta_n_271299.html New CIA Docs Detail Brutal 'Extraordinary Rendition' Process]". ''[[Huffington Post]]''. August 28, 2009.</ref><ref>{{cite news |title='A heavy price': Two decades of war, wariness and the post-9/11 security state |url=https://www.nbcnews.com/politics/national-security/heavy-price-two-decades-war-wariness-post-9-11-security-n1278846 |publisher=NBC News |date=September 10, 2021}}</ref>

=== Legal proceedings ===
{{Main|Trials related to the September 11 attacks|United States v. Khalid Sheikh Mohammed}}
As all 19 hijackers died in the attacks, they were never prosecuted. Osama bin Laden was never formally indicted but was after a [[Manhunt for Osama bin Laden|10-year manhunt]] [[Killing of Osama bin Laden|killed]] by U.S. special forces on May 2, 2011, in [[Osama bin Laden's compound in Abbottabad|his compound]] in [[Abbottabad]], Pakistan.{{Efn|President [[Barack Obama]] announced his death on May 1. At the time of the raid, it was early morning of May 2 in Pakistan and late afternoon of May 1 in the U.S.}}<ref>{{cite news |last1=Baker |first1=Peter |last2=Cooper |first2=Helene |date=May 1, 2011 |title=Bin Laden Is Dead, President Obama Says |work=[[The New York Times]] |url=https://www.nytimes.com/2011/05/02/world/asia/osama-bin-laden-is-killed.html |access-date=September 3, 2011}}</ref> The [[United States v. Khalid Sheikh Mohammed|main trial of the attacks]] against Mohammed and his co-conspirators [[Walid bin Attash]], [[Ramzi bin al-Shibh]], [[Ammar al-Baluchi]], and [[Mustafa Ahmad al Hawsawi]] remains unresolved. Khalid Sheikh Mohammed was arrested on March 1, 2003, in [[Rawalpindi]], Pakistan, by Pakistani security officials working with the CIA. He was then held at multiple [[Black site|CIA secret prisons]] and [[Guantanamo Bay detention camp|Guantanamo Bay]], where he was interrogated and tortured with methods including [[waterboarding]].<ref>{{cite news |last1=Shannon |first1=Elaine |last2=Weisskopf |first2=Michael |date=March 24, 2003 |title=Khalid Sheikh Mohammed Names Names |magazine=[[Time (magazine)|Time]] |url=http://content.time.com/time/nation/article/0,8599,436061,00.html |access-date=September 3, 2011 |archive-date=September 27, 2019 |archive-url=https://web.archive.org/web/20190927221045/http://content.time.com/time/nation/article/0,8599,436061,00.html |url-status=dead }}</ref><ref>{{cite news |last=Nichols |first=Michelle |date=May 8, 2008 |title=US judge orders CIA to turn over 'torture' memo-ACLU |publisher=[[Reuters]] |url=https://www.reuters.com/article/idUSN08420997 |access-date=September 3, 2011}}</ref> In 2003, [[Mustafa al-Hawsawi]] and [[Ammar al-Baluchi|Abd al-Aziz Ali]] were arrested and transferred to U.S. custody. Both would later be accused of providing money and travel assistance to the hijackers.<ref>{{Cite web |last=Rosenberg |first=Carol |date=July 10, 2023 |title=Trial Guide: The Sept. 11 Case at Guantánamo Bay |url=https://www.nytimes.com/article/september-11-trial-guantanamo-bay.html |website=[[The New York Times]]}}</ref> During U.S. hearings at Guantanamo Bay in March 2007, Mohammed again confessed his responsibility for the attacks, stating he "was responsible for the 9/11 operation from A to Z" and that his statement was not made under duress.<ref name="aljazeera2007" /><ref>{{cite news |date=March 15, 2007 |title=Key 9/11 suspect 'admits guilt' |publisher=[[BBC News]] |url=http://news.bbc.co.uk/2/hi/americas/6452573.stm |access-date=April 10, 2012}}</ref> In January 2023, the US government opened up about a potential [[Plea bargain|plea deal]],<ref name=":1">{{Cite web |last=Dunleavy |first=Jerry |date=January 9, 2023 |title=9/11 trial delayed again as Biden administration pushes for plea deal with terrorists |url=https://www.washingtonexaminer.com/news/justice/2023-kicks-off-911-gitmo-hearings-delayed-again |access-date=December 20, 2023 |website=Washington Examiner |language=en}}</ref> with Biden giving up on the effort in September that year.<ref>{{Cite web |last1=Nagle |first1=Molly |last2=Schulze |first2=Elizabeth |last3=Winsor |first3=Morgan |title=Biden rejects proposed conditions for plea deal for 9/11 defendants |url=https://abcnews.go.com/Politics/biden-rejects-proposed-conditions-plea-deal-911-defendants/story?id=102989534 |date=September 7, 2023 |access-date=December 20, 2023 |website=[[ABC News (United States)|ABC News]] |language=en}}</ref>

To date, only peripheral persons have thus been convicted for charges in connection with the attacks. These include:

* [[Zacarias Moussaoui]] who was indicted in December 2001 and sentenced to life in prison without the possibility of parole in May 2006 by a U.S. federal jury
* [[Mounir el-Motassadeq|Mounir El Motassadeq]] who was first convicted in February 2003 by a [[Federal Court of Justice]] in Germany and was deported to [[Morocco]] in October 2018 after serving his sentence<ref>{{Cite web |last=Werkhäuser |first=Nina |title=Germany deports convicted 9/11 accomplice |url=https://www.dw.com/en/germany-deports-convicted-9-11-accomplice-motassadeq-to-morocco/a-45838887 |date=October 15, 2018 |access-date=December 20, 2023 |website=dw.com |language=en}}</ref>
* [[Abu Dahdah]] who was arrested in November 2001, sentenced by a [[Audiencia Nacional|Spanish High Court]] and released from prison in May 2013.<ref>{{Cite web |date=May 23, 2013 |title=Alleged Al Qaeda in Spain chief Abu Dahdah released - Spain |url=http://www.ansamed.info/ansamed/en/news/nations/spain/2013/05/23/Alleged-Qaeda-Spain-chief-Abu-Dahdah-released_8754650.html |website=ANSAMed |url-status=dead |archive-url=https://web.archive.org/web/20130524161926/https://www.ansa.it/ansamed/en/news/nations/spain/2013/05/23/Alleged-Qaeda-Spain-chief-Abu-Dahdah-released_8754650.html |archive-date=May 24, 2013 |access-date=December 20, 2023}}</ref><!--Please add a summary of the period between 2008 and 2023. See the heading "Trial for role in 9/11 attacks" in Mohammed's article and "United States v. Khalid Sheikh Mohammed" for information-->
On July 31, 2024, ''The New York Times'' reported that Mohammed, Walid bin Attash and Mustafa al-Hawsawi agreed to plead guilty to conspiracy in exchange for life sentences, avoiding trial and execution. However, on August 2, 2024, US Defense Secretary [[Lloyd Austin]] revoked a plea agreement with Mohammed.<ref>{{cite news|title=Plea deal for accused 9/11 plotters revoked by US defence secretary |date=August 3, 2024 |url=https://www.france24.com/en/americas/20240803-us-scraps-plea-deal-with-9-11-mastermind-and-two-other-defendants |archive-url=https://web.archive.org/web/20240803103006/https://www.france24.com/en/americas/20240803-us-scraps-plea-deal-with-9-11-mastermind-and-two-other-defendants |archive-date=August 3, 2024 |access-date=August 3, 2024}}</ref>

== Investigations ==
=== FBI ===
{{further|Hijackers in the September 11 attacks}}

Immediately after the attacks, the [[Federal Bureau of Investigation]] started [[PENTTBOM]], the largest criminal inquiry in US history. At its height, more than half of the FBI's agents worked on the investigation and followed a half-million leads.<ref name='Pentbomb'>{{cite web |url=https://www.fbi.gov/about-us/history/famous-cases/9-11-investigation/9-11-investigation |archive-url=https://web.archive.org/web/20101010030053/http://www.fbi.gov/about-us/history/famous-cases/9-11-investigation/9-11-investigation |url-status=dead |archive-date=October 10, 2010 |title=9/11 Investigation (PENTTBOM) |access-date=April 11, 2012 |publisher=[[Federal Bureau of Investigation]]}}</ref> The FBI concluded that there was "clear and irrefutable" evidence linking Al-Qaeda and bin Laden to the attacks.<ref>{{cite web|title=Testimony of Dale L. Watson, Executive Assistant Director, Counterterrorism/Counterintelligence Division, FBI Before the Senate Select Committee on Intelligence|date=February 6, 2002|url=https://www.fbi.gov/congress/congress02/watson020602.htm |publisher=[[Federal Bureau of Investigation]]|access-date=September 4, 2011 |archive-url=https://web.archive.org/web/20100410013616/http://www.fbi.gov/congress/congress02/watson020602.htm |archive-date=April 10, 2010 |url-status=dead}}</ref>

[[File:Mohamed Atta.jpg|thumb|upright|alt=Mohamed Atta headshot, expressionless, full face |[[Mohamed Atta]] was one of the main planners of the attacks and the operational leader, responsible for crashing Flight 11 into the North Tower.]]

The FBI quickly identified the hijackers, including leader Mohamed Atta, when his luggage was discovered at Boston's Logan Airport. Atta had been forced to check two of his three bags due to space limitations on the 19-seat commuter flight he took to Boston. Due to a new policy instituted to prevent flight delays, the luggage failed to make it aboard American Airlines Flight 11 as planned. The luggage contained the hijackers' names, assignments, and Al-Qaeda connections. "It had all these Arab-language{{sic}} papers that amounted to the Rosetta stone of the investigation", said one FBI agent.<ref name="Unraveling 9-11 Was in the Bags">{{cite news |title=Unraveling 9–11 Was in the Bags |date=February 6, 2009 |url=http://www.securityinfowatch.com/news/10555883/unraveling-9-11-was-in-the-bags |work=Newsday |access-date=April 11, 2012}}</ref> Within hours of the attacks, the FBI released the names and in many cases the personal details of the suspected pilots and hijackers.{{sfnp|Clarke|2004|pp=13–14}}<ref name="FBI 19">{{cite web |title=FBI Announces List of 19 Hijackers |publisher=Federal Bureau of Investigation |url=https://www.fbi.gov/news/pressrel/press-releases/fbi-announces-list-of-19-hijackers |access-date=September 4, 2011}}</ref> Abu Jandal, who served as bin Laden's chief bodyguard for years, confirmed the identity of seven hijackers as Al-Qaeda members during interrogations with the FBI on September 17. He had been jailed in a Yemeni prison since 2000.<ref>{{cite book |last=Bergen |first=Peter |author-link=Peter Bergen |year=2012 |title=Manhunt: The Ten-Year Search for Bin Laden – from 9/11 to Abbottabad |url=https://books.google.com/books?id=U7SriggSMckC&pg=PA29 |location=New York |publisher=Broadway Paperbacks |isbn=978-0-307-95588-3 |pages=29–30}}</ref><ref>{{cite book |last1=Soufan |first1=Ali |author-link1=Ali Soufan |last2=Freedman |first2=Daniel |year=2020 |title=The Black Banners (Declassified): How Torture Derailed the War on Terror after 9/11 |url=https://books.google.com/books?id=1tTXDwAAQBAJ&pg=PT302 |location=New York |publisher=W. W. Norton & Company |isbn=978-0-393-54072-7 |pages=317–318}}</ref> On September 27, 2001, photos of all 19 hijackers were released, along with information about possible nationalities and aliases.<ref>{{cite web|title=The FBI Releases 19 Photographs of Individuals Believed to be the Hijackers of the Four Airliners that Crashed on September 11, 2001|url=https://www.fbi.gov/news/pressrel/press-releases/the-fbi-releases-19-photographs-of-individuals-believed-to-be-the-hijackers|publisher=Federal Bureau of Investigation|access-date=September 4, 2011}}</ref> Fifteen of the men were from Saudi Arabia, two were from the [[United Arab Emirates]], one was from Egypt, and one was from Lebanon.<ref>{{cite news |last=Johnston |first=David|title=Two Years Later: 9/11 Tactics; Official Says Qaeda Recruited Saudi Hijackers to Strain Ties|url=https://www.nytimes.com/2003/09/09/us/two-years-later-9-11-tactics-official-says-qaeda-recruited-saudi-hijackers.html|access-date=September 4, 2011 |newspaper=The New York Times|date=September 9, 2003}}</ref>

By midday, the U.S. National Security Agency and German intelligence agencies had intercepted communications pointing to Osama bin Laden.<ref>{{cite news |title=Piece by piece, the jigsaw of terror revealed |url=https://www.independent.co.uk/news/world/americas/piece-by-piece-the-jigsaw-of-terror-revealed-671334.html|archive-url=https://web.archive.org/web/20091015065134/http://www.independent.co.uk/news/world/americas/piece-by-piece-the-jigsaw-of-terror-revealed-671334.html|archive-date=October 15, 2009|access-date=September 4, 2011 |newspaper=The Independent|date=September 30, 2001 |location=London}}</ref> Two of the hijackers were known to have traveled with a bin Laden associate to Malaysia in 2000<ref>[http://avalon.law.yale.edu/sept11/911Report.pdf ''9/11 Commission Report''] pp. 266–272</ref> and hijacker [[Mohamed Atta]] had previously gone to Afghanistan.<ref>[https://web.archive.org/web/20121109021924/http://www.time.com/time/magazine/article/0%2C9171%2C1000987-2%2C00.html The Manhunt Goes Global] Time magazine October 15, 2001</ref> He and others were part of a terrorist cell in [[Hamburg]].<ref>{{cite news |first1=John |last1=Tagliabue |last2=Bonner |first2=Raymond |url=https://www.nytimes.com/2001/09/29/world/nation-challenged-german-intelligence-german-data-led-us-search-for-more-suicide.html|title=A Nation challenged: German Intelligence; German Data Led U.S. to Search For More Suicide Hijacker Teams |work=The New York Times |date=September 29, 2001 |access-date=September 4, 2011}}</ref> One of the members of the [[Hamburg cell]] in Germany was discovered to have been in communication with [[Khalid Sheikh Mohammed]] who was identified as a member of [[Al-Qaeda]].<ref>[http://avalon.law.yale.edu/sept11/911Report.pdf ''9/11 Commission Report''] pp. 276–277</ref>

Authorities in the United States and the United Kingdom also obtained electronic intercepts, including telephone conversations and electronic bank transfers, which indicated that [[Mohammed Atef]], a bin Laden deputy, was a key figure in the planning of the 9/11 attacks. Intercepts were also obtained of conversations that took place days before September 11 between bin Laden and an associate in Pakistan referring to "an incident that would take place in America on, or around, September 11" and discussing potential repercussions. In another conversation with an associate in Afghanistan, bin Laden discussed the "scale and effects of a forthcoming operation". These conversations did not specifically mention the World Trade Center, the Pentagon, or other specifics.<ref>{{cite news |title=The proof they did not reveal |work=Sunday Times |date=October 7, 2001|url=http://www.sunday-times.co.uk/news/pages/sti/2001/10/07/stiusausa02012.html|archive-url=https://web.archive.org/web/20011116020322/http://www.sunday-times.co.uk/news/pages/sti/2001/10/07/stiusausa02012.html|archive-date=November 16, 2001}}</ref>

{{anchor|Origins}}{{Bar chart
| title = Origins of [[Hijackers in the September 11 attacks|the 19 hijackers]]
| label_type = Nationality
| data_type = Number
| bar_width = 20
| width_units = em
| data_max = 19
| label1 = [[Saudi Arabia]]
| data1 = 15
| label2 = [[United Arab Emirates]]
| data2 = 2
| label3 = [[Egypt]]
| data3 = 1
| label4 = [[Lebanon]]
| data4 = 1
}}

In their annual violent crime index for the year 2001, the FBI recorded the deaths from the attacks as murder, in separate tables so as not to mix them with other reported crimes for that year.<ref>{{Cite web |date=October 28, 2002 |title=Crime in the United States 2001, Section V |url=https://ojjdp.ojp.gov/ojstatbb/ezacjrp/pdf/cius_911.pdf |access-date=April 13, 2023 |publisher=[[Federal Bureau of Investigation]]}}</ref> In a disclaimer, the FBI stated that "the number of deaths is so great that combining it with the traditional [[crime statistics]] will have an [[outlier]] effect that falsely [[skewness|skews]] all types of measurements in the program's analyses".<ref>{{cite web|url=https://ucr.fbi.gov/crime-in-the-u.s/2001/toc01.pdf|title=Crime in the United States 2001|publisher=[[Federal Bureau of Investigation]]|date=October 28, 2002|page=2|access-date=September 12, 2018}}</ref> New York City also did not include the deaths in their annual crime statistics for 2001.<ref name="HuffPost story">{{cite news|last=Hanrahan|first=Mark|title=Henryk Siwiak, Shot To Death On September 11th: Case Remains Unsolved|url=http://www.huffingtonpost.com/2011/09/08/911-only-homicide-unsolved_n_953864.html|newspaper=[[Huffington Post]]|date=September 8, 2011|access-date=September 6, 2016}}</ref>

=== CIA ===
{{Further|September 11 intelligence before the attacks}}
In 2004, [[John L. Helgerson]], the Inspector General of the [[Central Intelligence Agency]] (CIA), conducted an internal review of the agency's pre-9/11 performance and was harshly critical of senior CIA officials for not doing everything possible to confront terrorism.<ref name="Spiegel 2009">{{cite news |title=Ex-CIA Inspector General on Interrogation Report: 'The Agency Went over Bounds and Outside the Rules' |website=Der Spiegel |date=August 31, 2009 |url=https://www.spiegel.de/international/world/ex-cia-inspector-general-on-interrogation-report-the-agency-went-over-bounds-and-outside-the-rules-a-646010.html |access-date=February 3, 2021}}</ref> According to [[Philip Giraldi]] in ''[[The American Conservative]]'', Helgerson criticized their failure to stop two of the 9/11 hijackers, Nawaf al-Hazmi and Khalid al-Mihdhar, as they entered the United States and their failure to share information on the two men with the FBI.<ref>{{cite magazine |url=http://www.theamericanconservative.com/articles/deep-background/|title=Deep Background |magazine=American Conservative |date=April 1, 2005 |access-date=April 11, 2012}}</ref>

In May 2007, senators from both major U.S. political parties (the [[Republican Party (United States)|Republican]] and [[Democratic Party (United States)|Democratic]] parties) drafted legislation to make the review public. One of the backers, Senator [[Ron Wyden]] said, "The American people have a right to know what the Central Intelligence Agency was doing in those critical months before 9/11".<ref>{{cite news|first=Katherine |last=Shrader |title=Senators Want CIA to Release 9/11 Report |url=http://www.sfgate.com/cgi-bin/article.cgi?f=/n/a/2007/05/17/national/w131436D49.DTL |work=San Francisco Chronicle |agency=Associated Press |date=May 17, 2007 |access-date=September 4, 2011 |archive-url=https://web.archive.org/web/20071017005618/http://www.sfgate.com/cgi-bin/article.cgi?f=%2Fn%2Fa%2F2007%2F05%2F17%2Fnational%2Fw131436D49.DTL |archive-date=October 17, 2007 |url-status=dead}}</ref> The report was released in 2009 by President [[Barack Obama]].<ref name="Spiegel 2009" />

=== Congressional inquiry ===
{{Main|Joint Inquiry into Intelligence Community Activities before and after the Terrorist Attacks of September 11, 2001}}
In February 2002, the [[Senate Select Committee on Intelligence]] and the [[House Permanent Select Committee on Intelligence]] formed a joint inquiry into the performance of the [[U.S. Intelligence Community]].<ref>[http://www.intelligence.senate.gov/press/record.cfm?id=263577 Press Release of Intelligence Committee], Senate and House Intelligence Committees Announce Joint Inquiry into the September 11 Terrorist Attacks, February 14, 2002.</ref> Their 832-page report released in December 2002<ref>{{cite web|url=http://www.gpoaccess.gov/serialset/creports/911.html |title=Congressional Reports: Joint Inquiry into Intelligence Community Activities before and after the Terrorist Attacks of September 11, 2001 |access-date=August 10, 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100807204747/http://www.gpoaccess.gov//serialset/creports/911.html |archive-date=August 7, 2010}}</ref> detailed failings of the FBI and CIA to use available information, including about terrorists the CIA knew were in the United States, to disrupt the plots.<ref name="Theoharis 2006 p222–224">{{cite book |editor-first=Athan G. |editor-last=Theoharis |title=The Central Intelligence Agency: Security Under Scrutiny |publisher=[[Greenwood Publishing Group]] |pages=[https://books.google.com/books?id=-nj4RLdHCU0C&pg=PA223 222–224] |year=2006 |isbn=0-313-33282-7}}</ref> The joint inquiry developed its information about possible involvement of Saudi Arabian government officials from non-classified sources.<ref name="McClatchy DC 2013-08-12">{{cite news |first=Ali |last=Watkins |url=http://www.mcclatchydc.com/2013/08/12/199122_senate-intelligence-panel-could.html?rh=1 |title=Senate intelligence panel could seek to declassify documents; it just doesn't |archive-url=https://web.archive.org/web/20140903123631/http://www.mcclatchydc.com/2013/08/12/199122_senate-intelligence-panel-could.html|archive-date=September 3, 2014 |publisher=[[The McClatchy Company|McClatchy Washington Bureau]] |date=August 12, 2013}}</ref> The Bush administration demanded 28 related pages remain classified.<ref name="Theoharis 2006 p222–224" /> In December 2002, the inquiry's chair [[Bob Graham]] revealed in an interview that there was "evidence that there were foreign governments involved in facilitating the activities of at least some of the terrorists in the United States".<ref>[https://www.pbs.org/newshour/bb/politics-july-dec02-intelligence_12-11/ Improving Intelligence], [[PBS]] interview with Sen. Bob Graham, December 11, 2002.</ref> September 11 victim families were frustrated by the unanswered questions and redacted material from the congressional inquiry and demanded an independent commission.<ref name="Theoharis 2006 p222–224" /> September 11 victim families,<ref>{{cite news |first=Chris |last=Mondics |url=http://articles.philly.com/2014-03-31/business/48708504_1_osama-president-obama-law-firm |archive-url=https://web.archive.org/web/20140407230637/http://articles.philly.com/2014-03-31/business/48708504_1_osama-president-obama-law-firm |url-status=dead |archive-date=April 7, 2014 |title=Struggling to detail alleged Saudi role in 9/11 attacks |work=[[Philadelphia Inquirer]] |date=March 31, 2014}}</ref> members of Congress<ref>[https://jones.house.gov/sites/jones.house.gov/files/Reps.%20Jones%20and%20Lynch%20Letter%20to%20Obama_28%20Pages.pdf April 10, 2014 Letter to Barack Obama] {{Webarchive|url=https://web.archive.org/web/20160907084340/http://jones.house.gov/sites/jones.house.gov/files/Reps.%20Jones%20and%20Lynch%20Letter%20to%20Obama_28%20Pages.pdf |date=September 7, 2016 }}, signed by Representatives [[Walter B. Jones Jr.]] and [[Stephen Lynch (politician)|Stephen Lynch]].</ref> and the Saudi Arabian government are still seeking the release of the documents.<ref>{{cite news |first=Jake |last=Tapper |author-link=Jake Tapper |url=http://thelead.blogs.cnn.com/2014/09/08/why-hasnt-obama-kept-promise-to-declassify-28-pages-about-911 |title=Why hasn't Obama kept a promise to declassify 28 pages of a report about 9/11? |publisher=[[CNN]] |date=September 8, 2014 |access-date=September 12, 2014 |archive-date=August 3, 2021 |archive-url=https://web.archive.org/web/20210803143353/https://thelead.blogs.cnn.com/2014/09/08/why-hasnt-obama-kept-promise-to-declassify-28-pages-about-911/ |url-status=dead }}</ref><ref>{{cite magazine |title=The Twenty-Eight Pages |magazine=[[The New Yorker]] |first=Lawrence |last=Wright |url=http://www.newyorker.com/news/daily-comment/twenty-eight-pages |date=September 9, 2014 |access-date=August 30, 2019}}</ref> In June 2016, CIA chief [[John O. Brennan|John Brennan]] said that he believes 28 redacted pages of a congressional inquiry into 9/11 will soon be made public, and that they will prove that the government of Saudi Arabia had no involvement in the September 11 attacks.<ref>{{cite news |first=Euan |last=McKirdy |url=http://edition.cnn.com/2016/06/12/politics/cia-john-brennan-saudi-arabia-9-11/ |title=CIA chief: Missing report pages exonerate Saudi Arabia in 9/11 attacks |publisher=[[CNN]] |date=June 14, 2016}}</ref>

In September 2016, Congress passed the [[Justice Against Sponsors of Terrorism Act]] that would allow relatives of victims of the September 11 attacks to sue [[Saudi Arabia]] for its government's [[Alleged Saudi government role in the September 11 attacks|alleged role in the attacks]].<ref>"[https://www.usatoday.com/story/news/politics/2016/09/23/obama-veto-terrorism-lawsuit-bill-setting-up-override-battle/90407496/ Why Obama doesn't want 9/11 families suing Saudi Arabia]". ''USA Today''. September 23, 2016.</ref><ref>"[http://www.nydailynews.com/news/world/saudi-arabia-warns-750b-response-9-11-liability-suit-article-1.2603675 Saudi Arabia threatens to pull $750B from U.S. economy if Congress allows them to be sued for 9/11 terror attacks]". ''Daily News'' (New York). April 16, 2016.</ref><ref>"[http://www.nydailynews.com/news/world/saudi-government-didn-fund-terrorists-obama-aide-article-1.2605678 Mayor de Blasio joins Democrats in calling on President Obama to go after Saudi Arabia on 9/11 ties]". ''Daily News'' (New York). April 19, 2016.</ref>

===9/11 Commission===
{{Main|9/11 Commission|9/11 Commission Report}}
{{See also|Criticism of the 9/11 Commission}}
[[File:911report cover HIGHRES.png|thumb|The cover of the ''[[9/11 Commission Report]]'', a 585-page report released in 2004, on events leading up to the September 11 attacks and steps recommended to avoid a future terrorist attack]]
The National Commission on Terrorist Attacks Upon the United States, popularly known as the [[9/11 Commission]], chaired by [[Thomas Kean]],{{efn|Former Secretary of State [[Henry Kissinger]] was initially appointed to head the commission<ref>{{cite news|url=https://www.pbs.org/newshour/bb/terrorism/july-dec02/investigation_11-27.html|title=Investigating Sept. 11|publisher=PBS|work=NewsHour|date=November 27, 2002|access-date=January 21, 2009|url-status=dead|archive-url= https://web.archive.org/web/20090220061250/http://www.pbs.org/newshour/bb/terrorism/july-dec02/investigation_11-27.html|archive-date= February 20, 2009}}</ref> but resigned only weeks after being appointed, to avoid conflicts of interest.<ref>{{cite news|publisher=[[Cable News Network]]|url= http://archives.cnn.com/2002/ALLPOLITICS/12/13/kissinger.resigns/|title=Kissinger resigns as head of 9/11 commission |date=December 13, 2002|access-date=August 7, 2006|url-status=dead|archive-url= https://web.archive.org/web/20060427145915/http://archives.cnn.com/2002/ALLPOLITICS/12/13/kissinger.resigns/|archive-date=April 27, 2006}}</ref> Former U.S. Senator [[George J. Mitchell|George Mitchell]] was originally appointed as the vice chairman, but he stepped down on December 10, 2002, not wanting to sever ties to his law firm.<ref>{{cite news |url=http://archives.cnn.com/2002/ALLPOLITICS/12/11/mitchell.resigns/ |title=Mitchell quits 9/11 probe |date=December 10, 2002 |publisher=CNN |access-date=January 21, 2009| archive-url= https://web.archive.org/web/20090220082114/http://archives.cnn.com/2002/ALLPOLITICS/12/11/mitchell.resigns/| archive-date= February 20, 2009 | url-status= live}}</ref> On December 15, 2002, Bush appointed former [[New Jersey]] Governor [[Thomas Kean|Tom Kean]] to head the commission.<ref>{{cite news |url=http://archives.cnn.com/2002/ALLPOLITICS/12/16/commission.kean/ |title=Bush taps ex-New Jersey governor for 9/11 panel |date=December 16, 2002 |publisher=CNN |access-date=January 21, 2009| archive-url= https://web.archive.org/web/20090220082119/http://archives.cnn.com/2002/ALLPOLITICS/12/16/commission.kean/| archive-date= February 20, 2009 | url-status= live}}</ref>}} was formed in late 2002 to prepare a thorough account of the circumstances surrounding the attacks, including preparedness for and the immediate response to the attacks.<ref>{{cite web|url=http://govinfo.library.unt.edu/911/about/bio_kean.htm|title=National Commission on Terrorist Attacks Upon the United States|publisher=govinfo.library.unt.edu|access-date=September 4, 2011}}</ref> On July 22, 2004, the commission issued the ''[[9/11 Commission Report]]'', a 585-page report based on its investigations. The report detailed the events leading up to the attacks, concluding that they were carried out by [[Al-Qaeda]].<ref>{{cite web |url=https://www.9-11commission.gov/report/911Report.pdf |title=The 9/11 Commission Report |date=July 22, 2004 |access-date=August 23, 2024}}</ref> The commission also examined how security and intelligence agencies were inadequately coordinated to prevent the attacks.

According to the report, "We believe the 9/11 attacks revealed four kinds of failures: in imagination, policy, capabilities, and management".<ref>{{cite web |title=Foresight-and Hindsight |url=http://www.9-11commission.gov/report/911Report_Ch11.htm |publisher=National Commission on Terrorist Attacks Upon the United States |access-date=September 4, 2011}}</ref> The commission made numerous recommendations on how to prevent future attacks, and in 2011 was dismayed that several of its recommendations had yet to be implemented.<ref>{{cite news |last=Bennett |first=Brian |title=Post-9/11 assessment sees major security gaps |url=https://www.latimes.com/nation/la-xpm-2011-aug-30-la-na-911-report-card-20110831-story.html |newspaper=Los Angeles Times |date=August 30, 2011 |access-date=September 4, 2011}}</ref>

=== National Institute of Standards and Technology ===
{{Main|NIST World Trade Center Disaster Investigation}}
{{See also|7 World Trade Center (1987–2001)#9/11 and collapse}}
[[File:WTC-Wreckage-exterior shell of south tower.jpg|thumb|The exterior support columns from the lower level of the South Tower remained standing after the [[Collapse of the World Trade Center|building collapsed]].]]
The U.S. [[National Institute of Standards and Technology]] (NIST) investigated the collapses of the Twin Towers and 7{{spaces}}WTC. The investigations examined why the buildings collapsed and what fire protection measures were in place, and evaluated how fire protection systems might be improved in future construction.<ref name="NISTInvest">{{cite press release |title=NIST's World Trade Center Investigation |publisher=National Institute of Standards and Technology |date=September 8, 2006 |url=https://www.nist.gov/news-events/news/2006/09/nists-world-trade-center-investigation |access-date=September 4, 2011}}</ref> The investigation into the collapse of 1{{spaces}}WTC and 2{{spaces}}WTC was concluded in October 2005 and that of 7{{spaces}}WTC was completed in August 2008.<ref name="NIST WTC 7 Investigation">{{cite press release |title=NIST WTC 7 Investigation Finds Building Fires Caused Collapse |date=August 21, 2008 |publisher=The National Institute of Standards and Technology |url=https://www.nist.gov/news-events/news/2008/08/nist-wtc-7-investigation-finds-building-fires-caused-collapse |access-date=September 4, 2011}}</ref>

NIST found that the fireproofing on the Twin Towers' steel infrastructures was blown off by the initial impact of the planes and that had this not occurred, the towers likely would have remained standing.<ref name="NISTCollapse">{{cite book|author=National Construction Safety Team |chapter-url=https://www.nist.gov/customcf/get_pdf.cfm?pub_id=909017 |title=Final Report on the Collapse of the World Trade Center Towers |publisher=National Institute of Standards and Technology, United States Department of Commerce |chapter=Executive Summary |date=September 2005 |access-date=April 10, 2011 |chapter-format=PDF}}</ref> A 2007 study of the north tower's collapse published by researchers of [[Purdue University]] determined that since the plane's impact had stripped off much of the structure's thermal insulation, the heat from a typical office fire would have softened and weakened the exposed girders and columns enough to initiate the collapse regardless of the number of columns cut or damaged by the impact.<ref>{{cite journal|last1=Irfanoglu |first1=A.|last2=Hoffmann |first2=C. M.|doi=10.1061/(ASCE)0887-3828(2008)22:1(62)|title=Engineering Perspective of the Collapse of WTC-I|journal=Journal of Performance of Constructed Facilities|volume=22|page=62|year=2008|quote=As the aircraft debris went through several stories in the tower, much of the thermal insulation on the core columns would have been scoured off. Under such conditions, the ensuing fire would be sufficient to cause instability and initiate collapse. From an engineering perspective, impact damage to the core structure had a negligible effect on the critical thermal load required to initiate collapse in the core structure.}}</ref><ref>{{cite news|title=Purdue creates scientifically based animation of 9/11 attack|last=Tally|first=Steve|publisher=Purdue News Service|url=http://news.uns.purdue.edu/x/2007a/070612HoffmannWTC.html|date=June 12, 2007|access-date=September 4, 2011|quote=The aircraft moved through the building as if it were a hot and fast lava flow", Sozen says. "Consequently, much of the fireproofing insulation was ripped off the structure. Even if all of the columns and girders had survived the impact{{snd}}an unlikely event{{snd}}the structure would fail as the result of a buckling of the columns. The heat from an ordinary office fire would suffice to soften and weaken the unprotected steel. Evaluation of the effects of the fire on the core column structure, with the insulation removed by the impact, showed that collapse would follow whatever the number of columns cut at the time of the impact.|archive-date=December 31, 2018|archive-url=https://web.archive.org/web/20181231084252/https://news.uns.purdue.edu/x/2007a/070612HoffmannWTC.html|url-status=dead}}</ref>

The director of the original investigation stated that "the towers did amazingly well. The terrorist aircraft didn't bring the buildings down; it was the fire that followed. It was proven that you could take out two-thirds of the columns in a tower and the building would still stand".<ref name="TerrorProof">{{cite web|title=Building a Terror-Proof Skyscraper: Experts Debate Feasibility, Options |first=Pete |last=Sigmund |url=http://www.constructionequipmentguide.com/Building-a-Terror-Proof-Skyscraper-Experts-Debate-Feasibility-Options/2598/ |access-date=April 11, 2012 |date=September 25, 2002}}</ref> The fires weakened the trusses supporting the floors, making the floors sag. The sagging floors pulled on the exterior steel columns causing the exterior columns to bow inward.

With the damage to the core columns, the buckling exterior columns could no longer support the buildings, causing them to collapse. Additionally, the report found the towers' stairwells were not properly reinforced to provide adequate [[Fire escape|emergency escape]] for people above the impact zones.<ref name="NIST">{{cite web|title=Translating WTC Recommendations into Model Building Codes|publisher=National Institute of Standards and Technology|url=http://wtc.nist.gov/NIBS_MMC/CodeChangeProposals.htm|archive-url=https://web.archive.org/web/20110310004023/http://wtc.nist.gov/NIBS_MMC/CodeChangeProposals.htm|archive-date=March 10, 2011|access-date=September 4, 2011 |date=October 25, 2007}}</ref> NIST concluded that uncontrolled fires in 7{{spaces}}WTC caused floor beams and girders to heat and subsequently "caused a critical support column to fail, initiating a fire-induced progressive collapse that brought the building down".<ref name="NIST WTC 7 Investigation" />

=== Alleged Saudi government role ===
{{Main|Alleged Saudi government role in the September 11 attacks}}{{See also|Saudi Arabia–United States relations|Saudi Arabia and state-sponsored terrorism|The 28 pages}}
In July 2016, the Obama administration released a document compiled by U.S. investigators Dana Lesemann and Michael Jacobson, known as "File 17",<ref>{{cite news |title=Saudi diplomats 'links to 9/11 attackers' |url=https://www.thetimes.co.uk/article/saudi-diplomats-linked-to-9-11-plot-9hgrfjhbm |work=The Week |date=April 20, 2016}}</ref> which contains a list naming three dozen people, including the suspected [[General Intelligence Presidency|Saudi intelligence]] officers attached to Saudi Arabia's embassy in Washington, D.C.,<ref>{{cite news |title=US to reveal Saudi official allegedly tied to 9/11 attackers |url=https://www.aljazeera.com/news/2019/09/reveal-saudi-official-allegedly-tied-911-attackers-190913011926350.html |publisher=Al Jazeera |date=September 13, 2019}}</ref> which connects Saudi Arabia to the hijackers.<ref>{{cite news|last1=Riechmann|first1=Deb|title=File 17 Is Glimpse Into Still-Secret 28 Pages About 9/11|url=https://apnews.com/fe56c5d224a8463aa7cfc6ccf4689122 |publisher=Associated Press |date=July 2, 2016}}</ref><ref>{{cite news |title=CIA and Saudi Arabia Conspired to Keep 9/11 Details Secret, New Book Says |url=https://www.newsweek.com/cia-and-saudi-arabia-conspired-keep-911-details-secret-new-book-says-1091935 |work=Newsweek |date=August 28, 2018}}</ref>

In September 2016, Congress passed the [[Justice Against Sponsors of Terrorism Act]].<ref name="Stempel">{{cite news|last=Stempel|first=Jonathan|date=March 28, 2018|title=Saudi Arabia must face U.S. lawsuits over Sept. 11 attacks|url=https://www.reuters.com/article/us-usa-saudi-sept11/saudi-arabia-must-face-u-s-lawsuits-over-sept-11-attacks-idUSKBN1H43A1|publisher=Reuters|access-date=November 22, 2018}}</ref><ref>{{cite news|first1=Scott|last1=Horsley|first2=Alisa|last2=Chang|title=Senate Votes To Override Obama's Veto On Sept. 11 Lawsuit Bill|publisher=NPR|url=https://www.npr.org/2016/09/28/495709481/sept-11-lawsuits-vote-today-could-be-first-reversal-of-an-obama-veto|date=September 28, 2016}}</ref> The practical effect of the legislation was to allow the continuation of a longstanding civil lawsuit brought by families of victims of the September 11 attacks against Saudi Arabia for its government's alleged role in the attacks.<ref>{{cite web|title=S.2040 – Justice Against Sponsors of Terrorism Act|url=https://www.congress.gov/bill/114th-congress/senate-bill/2040|publisher=U.S. Congress |access-date=May 20, 2016}}</ref> In March 2018, a U.S. judge formally allowed a suit to move forward against the government of Saudi Arabia brought by 9/11 survivors and victims' families.<ref name="Stempel" />

In 2022, the families of some 9/11 victims obtained two videos and a notepad seized from Saudi national [[Omar al-Bayoumi]] by the British courts. The first video showed him hosting a party in [[San Diego]] for Nawaf al-Hazmi and Khalid al-Mihdhar, the first two hijackers to arrive in the U.S. The other video showed al-Bayoumi greeting the cleric [[Anwar al-Awlaki]], who was blamed for radicalizing Americans and later killed in a CIA drone strike. The notepad depicted a hand-drawn aeroplane and some mathematical equations that, according to a pilot's court statement, might have been used to calculate the rate of descent to get to a target. According to a 2017 FBI memo, from the late 1990s up until the 9/11 attack, al-Bayoumi was a paid cooptee of the Saudi [[General Intelligence Presidency]]. {{As of|2022|04}} he is believed to be living in Saudi Arabia, which has denied any involvement in 9/11.<ref>{{cite news |last1=Herridge |first1=Catherine |title=Newly released video shows 9/11 hijackers with alleged Saudi intelligence operative |url=https://www.cbsnews.com/news/911-hijackers-video-saudi-intelligence-official-omar-al-bayoumi/ |publisher=CBS News |date=April 27, 2022}}</ref>

== Rebuilding and memorials ==

=== Reconstruction ===
{{Main|Rescue and recovery effort after the September 11 attacks on the World Trade Center|Construction of One World Trade Center}}
{{Further|World Trade Center (2001–present)|World Trade Center site}}
[[File:Lower_Manhattan_from_Jersey_City_September_2020_HDR_panorama_(cropped).jpg|thumb|The [[World Trade Center (2001–present)|rebuilt World Trade Center]], September 2020]]
On the day of the attacks, New York City mayor Rudy Giuliani stated: "We will rebuild. We're going to come out of this stronger than before, politically stronger, economically stronger. The skyline will be made whole again".<ref>{{cite news |last=Taylor |first=Tess |url=http://www.architectureweek.com/2001/0926/today.html |title=Rebuilding in New York |date=September 26, 2001 |work=Architecture Week |issue=68 |access-date=September 4, 2011 |archive-url=https://web.archive.org/web/20110511012010/http://www.architectureweek.com/2001/0926/today.html |archive-date=May 11, 2011 |url-status=dead }}</ref>

Within hours of the attack, a substantial search and rescue operation was launched. After months of around-the-clock operations, the World Trade Center site was cleared by the end of May 2002.<ref>{{cite news |url=http://archives.cnn.com/2002/US/05/30/rec.wtc.cleanup/ |archive-url=https://web.archive.org/web/20081201081749/http://archives.cnn.com/2002/US/05/30/rec.wtc.cleanup/ |archive-date=December 1, 2008 |url-status=dead |title=Ceremony closes 'Ground Zero' cleanup |date=May 30, 2002 |publisher=CNN|access-date=November 24, 2013}}</ref> The damaged section of the Pentagon was rebuilt and occupied within a year of the attacks.<ref>{{cite news|last=Oglesby |first=Christy |title=Phoenix rises: Pentagon honors 'hard-hat patriots' |url=http://archives.cnn.com/2002/US/09/11/ar911.memorial.pentagon/ |publisher=CNN|date=September 11, 2002 |url-status=dead |archive-url=https://web.archive.org/web/20041218040531/http://archives.cnn.com/2002/US/09/11/ar911.memorial.pentagon/ |archive-date=December 18, 2004 |access-date=May 29, 2014}}</ref> The temporary [[World Trade Center (PATH station)|World Trade Center PATH station]] opened in late 2003 and construction of the new 7{{spaces}}World Trade Center was completed in 2006. Work on rebuilding the main World Trade Center site was delayed until late 2006 when leaseholder [[Larry Silverstein]] and the Port Authority of New York and New Jersey agreed on financing.<ref>{{cite news|url=https://www.nytimes.com/2006/09/22/nyregion/nyregionspecial3/22rebuild.html |title=An Agreement Is Formalized on Rebuilding at Ground Zero |work=The New York Times |last=Bagli |first=Charles V. |date=September 22, 2006|access-date=September 4, 2011}}</ref> The construction of [[One World Trade Center]] began on April 27, 2006, and reached its full height on May 20, 2013. The spire was installed atop the building at that date, putting One{{spaces}}WTC's height at 1,776 feet (541{{spaces}}m) and thus claiming the title of the tallest building in the [[Western Hemisphere]].<ref>{{cite news|url=http://www.nydailynews.com/new-york/1-wtc-spire-bringing-full-height-article-1.1340224|title=One World Trade Center gets spire, bringing it to its full 1,776-foot height|last1=Badia|first1=Erik|date=May 10, 2013|work=New York Daily News website|access-date=January 12, 2015|last2=Sit|first2=Ryan}}</ref><ref name="Moore One WTC">{{cite web |last=Moore |first=Jack |date=November 3, 2014 |title=World Trade Center Re-opens as Tallest Building in America |url=http://onewtc.com/news/world-trade-center-re-opens-as-tallest-building-in-america |url-status=dead |archive-url=https://web.archive.org/web/20150904120549/http://onewtc.com/news/world-trade-center-re-opens-as-tallest-building-in-america |archive-date=September 4, 2015 |access-date=September 11, 2015 |publisher=One World Trade Center}}</ref> One WTC finished construction and opened on November 3, 2014.<ref name="Moore One WTC" /><ref>{{cite news|url=http://time.com/3553897/one-world-trade-center-freedom-tower-opens-doors-new-york-city-911/|title=One World Trade Center Opens Its Doors|last=Iyengar|first=Rishi|date=November 3, 2014|magazine=Time|access-date=January 12, 2015}}</ref><ref>{{cite news |last=Smith |first=Aaron |date=November 3, 2014 |title=One World Trade Center opens today |publisher=CNN |url=https://money.cnn.com/2014/11/03/news/companies/one-world-trade-center/index.html |access-date=November 4, 2014}}</ref>

On the World Trade Center site, three more office towers were to be built one block east of where the original towers stood.<ref>{{cite web|title=Lower Manhattan: Current Construction |url=http://www.lowermanhattan.info/construction/project_updates/|archive-url=https://web.archive.org/web/20110914070256/http://www.lowermanhattan.info/construction/project_updates/|archive-date=September 14, 2011|publisher=Lower Manhattan Construction Command Center|access-date=September 8, 2011}}</ref> [[4 World Trade Center|4{{spaces}}WTC]], meanwhile, opened in November 2013, making it the second tower on the site to open behind 7{{spaces}}World Trade Center, as well as the first building on the Port Authority property.<ref>{{cite news|url=https://www.bloomberg.com/news/articles/2013-11-12/world-trade-center-tower-debuts-in-manhattan-leasing-test|title=NYC's World Trade Tower Opens 40% Empty in Revival|date=November 12, 2013|website=Bloomberg.com|access-date=October 5, 2015}}</ref> 3{{spaces}}WTC opened on June 11, 2018, becoming the fourth skyscraper at the site to be completed.<ref name="USAToday 2018-06-10">{{cite news|url=https://www.usatoday.com/story/news/nation/2018/06/10/3-world-trade-center-open-after-years-delays-twin-towers-site/689035002/|title=New World Trade Center to open after years of delays|date=June 10, 2018|website=USA Today|access-date=June 11, 2018}}</ref> In December 2022, the Nicholas Greek Orthodox Church fully reopened for regular services<ref name="CBS News 20222">{{cite web |date=December 6, 2022 |title=Saint Nicholas Greek Orthodox Church officially reopens to public after being destroyed on 9/11 |url=https://www.cbsnews.com/newyork/news/saint-nicholas-greek-orthodox-church-officially-reopens-to-public-after-being-destroyed-on-911/ |access-date=December 7, 2022 |website=CBS News}}</ref> followed by the opening of the [[Performing Arts Center (Manhattan)|Ronald O. Perelman Performing Arts Center]] in September 2023.<ref>{{Cite news |last=Pareles |first=Jon |date=September 18, 2023 |title=Perelman Arts Center Opens in New York and Welcomes the World |language=en-US |work=The New York Times |url=https://www.nytimes.com/2023/09/18/arts/music/perelman-arts-center-opens.html |access-date=September 27, 2023 |issn=0362-4331}}</ref> With construction beginning in 2008,<ref>{{Cite web |last=Dunlap |first=David W. |date=June 11, 2008 |title=Late Delivery of the 2 World Trade Center Site |url=http://cityroom.blogs.nytimes.com/2008/06/11/late-delivery-of-the-2-world-trade-center-site/ |url-status=live |archive-url=https://web.archive.org/web/20131206052142/http://cityroom.blogs.nytimes.com/2008/06/11/late-delivery-of-the-2-world-trade-center-site/ |archive-date=December 6, 2013 |access-date=April 24, 2014}}</ref> [[2 World Trade Center]] remains as of 2023 unfinished.<ref>{{Cite web |last=Sayej |first=Nadja |date=October 27, 2022 |title=The Latest Developments on 2 World Trade |url=https://lev.co/blog/markets/latest-development-2-world-trade/ |access-date=September 27, 2023 |website=Lev |language=en-US}}</ref> Construction of a [[5 World Trade Center]] is planned to begin in 2024 and be finished by 2029.<ref name=":02">{{Cite web |last=Rizzi |first=Nicholas |date=February 11, 2021 |title=Silverstein, Brookfield Win Bid to Build Tower at 5 World Trade Center |url=https://commercialobserver.com/2021/02/silverstein-brookfield-win-bid-to-build-mixed-use-tower-at-5-world-trade-center/ |url-status=live |archive-url=https://web.archive.org/web/20210213164618/https://commercialobserver.com/2021/02/silverstein-brookfield-win-bid-to-build-mixed-use-tower-at-5-world-trade-center/ |archive-date=February 13, 2021 |access-date=February 14, 2021 |website=Commercial Observer |language=en-US}}</ref><ref name="newyorkyimby.com">{{Cite web |last=Young |first=Michael |date=February 13, 2021 |title=Five World Trade Center's 900-Foot-Tall Redesign by Kohn Pedersen Fox Revealed, in Manhattan's Financial District |url=https://newyorkyimby.com/2021/02/five-world-trade-centers-900-foot-tall-redesign-by-kohn-pedersen-fox-revealed-in-manhattans-financial-district.html |url-status=live |archive-url=https://web.archive.org/web/20220421231413/https://newyorkyimby.com/2021/02/five-world-trade-centers-900-foot-tall-redesign-by-kohn-pedersen-fox-revealed-in-manhattans-financial-district.html |archive-date=April 21, 2022 |access-date=April 23, 2021 |website=New York YIMBY |language=en-US}}</ref>

=== Memorials ===
{{Main|Memorials and services for the September 11 attacks}}
[[File:9-11_Memorial_and_Museum_(28815276064).jpg|thumb|The [[National September 11 Memorial and Museum]] in [[Lower Manhattan]], August 2016]]
In the days immediately following the attacks, many memorials and vigils were held around the world, and photographs of the dead and missing were posted around [[World Trade Center site|Ground Zero]]. A witness described being unable to "get away from faces of innocent victims who were killed. Their pictures are everywhere, on phone booths, street lights, and walls of subway stations. Everything reminded me of a huge funeral, people were quiet and sad, but also very nice. Before, New York gave me a cold feeling; now people were reaching out to help each other".<ref>{{cite web |last=Sigmund |first=Pete |title=Crews Assist Rescuers in Massive WTC Search |url=http://www.constructionequipmentguide.com/Crews-Assist-Rescuers-in-Massive-WTC-Search/1531/ |publisher=Construction Equipment Guide |access-date=September 4, 2011}}</ref> President Bush proclaimed Friday, September 14, 2001, as Patriot Day.<ref>[https://georgewbush-whitehouse.archives.gov/news/releases/2001/09/20010913-7.html National Day of Prayer and Remembrance for the Victims Of the Terrorist Attacks on September 11, 2001] {{Webarchive|url=https://web.archive.org/web/20170906080819/https://georgewbush-whitehouse.archives.gov/news/releases/2001/09/20010913-7.html|date=September 6, 2017}} A Proclamation by the President of the United States of America</ref>
[[File:Lower_Manhattan_from_Jersey_City_September_2020_HDR.jpg|thumb|''[[Tribute in Light]]'', featuring two columns of light representing the Twin Towers, September 2020]]
One of the first memorials was the ''[[Tribute in Light]]'', an installation of 88 searchlights at the footprints of the World Trade Center towers.<ref>{{cite news |title=Tribute in light to New York victims |url=http://news.bbc.co.uk/2/hi/americas/1857699.stm |publisher=BBC News |date=March 6, 2002 |access-date=April 1, 2012}}</ref> In New York City, the [[World Trade Center Site Memorial Competition]] was held to design an appropriate memorial on the site.<ref>{{cite web |title=About the World Trade Center Site Memorial Competition |url=http://wtcsitememorial.org/about.html |publisher=World Trade Center Site Memorial Competition |access-date=September 4, 2011 |archive-date=December 15, 2018 |archive-url=https://web.archive.org/web/20181215163019/http://www.wtcsitememorial.org/about.html |url-status=dead }}</ref> The winning design, ''[[National September 11 Memorial & Museum|Reflecting Absence]]'', was selected in August 2006, and consists of a pair of reflecting pools in the footprints of the towers, surrounded by a list of the victims' names in an underground memorial space.<ref>{{cite news |agency=Associated Press |title=WTC Memorial Construction Begins|publisher=[[CBS News]]|date=March 6, 2006|url=https://www.cbsnews.com/news/wtc-memorial-construction-begins/|access-date=September 4, 2011}}</ref> The memorial was completed on September 11, 2011;<ref>{{cite web |url=http://www.nationalgeographic.com/remembering-9-11/place-of-remembrance/ |title=A Place of Remembrance |website=[[National Geographic (magazine)|National Geographic]] |year=2011 |access-date=November 5, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20141105175631/http://www.nationalgeographic.com/remembering-9-11/place-of-remembrance/ |archive-date=November 5, 2014 }}</ref> a museum also opened on site on May 21, 2014.<ref>{{cite news|url=http://www.myfoxny.com/story/25574078/national-september-11-memorial-museum-opens |title=National September 11 Memorial Museum opens |publisher=[[WNYW]] |date=May 21, 2014 |access-date=May 21, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140521194934/http://www.myfoxny.com/story/25574078/national-september-11-memorial-museum-opens |archive-date=May 21, 2014}}</ref>

''[[The Sphere]]'' by the German sculptor [[Fritz Koenig]] is the world's largest bronze sculpture of modern times, and stood between the Twin Towers on the [[Austin J. Tobin Plaza]] from 1971 until the attacks. The sculpture, weighing more than 20 tons, was the only remaining work of art to be recovered largely intact from the ruins of the towers. Since then, the work of art, known in the U.S. as ''The Sphere'', has been transformed into a symbolic monument of 9/11 commemoration. After being dismantled and stored near a hangar at [[John F. Kennedy International Airport]], the sculpture was the subject of the 2001 documentary ''[[The Sphere]]'' by filmmaker [[Percy Adlon]]. On August 16, 2017, the work was installed at [[Liberty Park]], close to the new World Trade Center aerial and the [[9/11 Memorial]].<ref name="NYT 2017-11-29">{{cite news |last=Otterman |first=Sharon |title=Battered and Scarred, 'Sphere' Returns to 9/11 Site |url=https://www.nytimes.com/2017/11/29/nyregion/911-memorial-sphere-sculpture.html |work=The New York Times |date=November 29, 2017 |access-date=August 23, 2021}}</ref>
[[File:US_Navy_080904-N-5319A-008_The_Pentagon_Memorial_honoring_the_184_people_killed_at_the_Pentagon_and_on_American_Airlines_flight_77.jpg|thumb|The [[National 9/11 Pentagon Memorial]] in [[Arlington County, Virginia]], September 2008]]

In Arlington County, the [[Pentagon Memorial]] was completed and opened to the public on the seventh anniversary of the attacks in 2008.<ref>{{cite news |last=Miroff |first=Nick |title=Creating a Place Like No Other |url=https://www.washingtonpost.com/wp-dyn/content/article/2008/09/10/AR2008091000018.html |newspaper=The Washington Post |date=September 11, 2008 |access-date=September 4, 2011}}</ref><ref>{{cite news |last=Miroff |first=Nick |title=A Long-Awaited Opening, Bringing Closure to Many |url=https://www.washingtonpost.com/wp-dyn/content/article/2008/09/11/AR2008091100579.html |newspaper=The Washington Post |date=September 12, 2008 |access-date=September 4, 2011}}</ref> It consists of a landscaped park with 184 benches facing the Pentagon.<ref name="dwyer-may2007">{{cite news |last=Dwyer |first=Timothy |title=Pentagon Memorial Progress Is Step Forward for Families |url=https://www.washingtonpost.com/wp-dyn/content/article/2007/05/25/AR2007052502284.html |newspaper=The Washington Post |date=May 26, 2007 |access-date=September 4, 2011}}</ref> When the Pentagon was repaired in 2001–2002, a private chapel and indoor memorial were included at the spot where Flight 77 crashed into the building.<ref>{{cite web |title=DefenseLINK News Photos – Pentagon's America's Heroes Memorial |url=http://www.defenselink.mil/photos/newsphoto.aspx?newsphotoid=4018 |url-status=dead |publisher=Department of Defense |access-date=September 4, 2011 |archive-url=https://web.archive.org/web/20091130081905/http://www.defenselink.mil/photos/newsphoto.aspx?newsphotoid=4018 |archive-date=November 30, 2009}}</ref>

In Shanksville, a [[Flight 93 National Memorial|concrete-and-glass visitor center]] was opened on September 10, 2015,<ref name="NPS 93 mem">{{cite web |title=Flight 93 National Memorial – Sources and Detailed Information |publisher=National Park Service |date=n.d. |url=https://www.nps.gov/flni/learn/historyculture/sources-and-detailed-information.htm |access-date=January 31, 2017 |quote=13. When will the Memorial be finished?}}</ref> situated on a hill overlooking the crash site and the white marble ''Wall of Names''.<ref name="NPS FAQs">{{cite web |title=Flight 93 National Memorial – Frequently Asked Questions (FAQs) |publisher=National Park Service |date=May 2013 |pages=22–23 |url=https://www.nps.gov/flni/historyculture/upload/FAQs_longform_formatted_5-2013.pdf |access-date=January 31, 2017}}</ref> An observation platform at the visitor centre and the white marble wall are both aligned beneath the path of Flight 93.<ref name="NPS FAQs" /><ref name="NYT 2015-09-09">{{cite news |title=A Long Road to a Place of Peace for Flight 93 Families |work=The New York Times |date=September 9, 2015 |url=https://www.nytimes.com/2015/09/09/us/a-long-road-to-a-place-of-peace-for-flight-93-families.html |access-date=September 9, 2015}}</ref> New York City firefighters donated a cross made of steel from the World Trade Center and mounted on top of a platform shaped like the Pentagon.<ref name='ap2008-08-24'>{{cite news |last=Nephin |first=Dan |title=Steel cross goes up near flight's 9/11 Pa. crash site |date=August 24, 2008 |agency=Associated Press |url=http://global.christianpost.com/news/steel-cross-installed-near-flight-93-site-in-pa-33978/ |access-date=September 5, 2011 |archive-date=October 21, 2011 |archive-url=https://web.archive.org/web/20111021140020/http://global.christianpost.com/news/steel-cross-installed-near-flight-93-site-in-pa-33978/ |url-status=dead }}</ref> It was installed outside the firehouse on August 25, 2008.<ref>{{cite news|last=Gaskell |first=Stephanie|title=Pa. site of 9/11 crash gets WTC beam |url=https://www.nytimes.com/2008/05/05/us/05memorial.html|date=August 25, 2008|work=New York Daily News|access-date=September 4, 2011}}</ref> Many other permanent memorials are elsewhere. Scholarships and charities have been established by the victims' families and by many other organizations and private figures.<ref>{{cite news|last=Fessenden|first=Ford |title=9/11; After the World Gave: Where $2 Billion in Kindness Ended Up|url=https://www.nytimes.com/2002/11/18/giving/9-11-after-the-world-gave-where-2-billion-in-kindness-ended-up.html|work=The New York Times|date=November 18, 2002|access-date=September 4, 2011}}</ref>

On every anniversary in New York City, the names of the victims who died there are read out over music. The President of the United States attends a memorial service at the Pentagon,<ref>{{cite news|url=http://cityroom.blogs.nytimes.com/2010/09/11/at-a-memorial-ceremony-loss-and-tension/?hp |work=The New York Times |title=At a Memorial Ceremony, Loss and Tension |first=Andy |last=Newman |date=September 11, 2010}}</ref> and asks Americans to observe [[Patriot Day]] with a moment of silence. Smaller services are held in Shanksville, Pennsylvania, which are usually attended by the First Lady. In September 2023, President Joe Biden did not attend services in the affected areas, instead marking the day in [[Anchorage, Alaska|Anchorage]], Alaska, the first U.S. President to do so since the attacks.<ref>{{Cite web |date=August 28, 2023 |title=Biden will observe 9/11 in Alaska instead of the traditional NYC, Virginia or Pennsylvania events |url=https://apnews.com/article/biden-911-terrorist-attack-harris-alaska-8e58378865dc612a49d0a2dee80f2304 |access-date=September 23, 2023 |website=AP News |language=en}}</ref><ref>{{Cite web |last=Judd |first=Donald |date=September 11, 2023 |title=Biden marks 9/11 in Alaska, calls on Americans 'to protect our democracy' {{!}} CNN Politics |url=https://www.cnn.com/2023/09/11/politics/biden-september-11-remarks/index.html |access-date=September 23, 2023 |website=CNN |language=en}}</ref><ref>{{Cite news |last=Hutzler |first=Alexandra |date=September 11, 2023 |title=Biden criticized for marking 9/11 anniversary in Alaska |work=[[ABC News (United States)|ABC News]] |url=https://abcnews.go.com/Politics/biden-mark-911-anniversary-alaska-harris-visits-ground/story?id=103088628 |access-date=September 23, 2023}}</ref>
{{clear}}

== See also ==
{{cmn|
* [[9/11 Commission]]
* ''[[9/11 Commission Report]]''
* [[Air France Flight 8969]]
* [[Bojinka plot]]
* [[Delta Air Lines Flight 1989|Delta 1989]] and [[Korean Air Flight 085|Korean 085]], two other flights that were falsely suspected of being hijacked as part of the September 11 attacks
* [[List of cultural references to the September 11 attacks]]
* [[Khobar Towers bombing]]
* [[List of attacks on U.S. territory]]
* [[List of aviation incidents involving terrorism]]
* [[List of deadliest terrorist attacks in the United States]]
* [[List of Islamist terrorist attacks]]
* [[List of major terrorist incidents]]
* [[List of terrorist incidents in 2001]]
* [[List of terrorist incidents in New York City]]
** [[Outline of the September 11 attacks]]
* [[Operation Yellow Ribbon]]
* [[Timeline of al-Qaeda attacks]]
* [[Timeline of the September 11 attacks]]
* [[USS Cole bombing|USS ''Cole'' bombing]]
* [[1993 World Trade Center bombing]]
* [[1998 United States embassy bombing]]
* [[2006 transatlantic aircraft plot]]
* [[2007 John F. Kennedy International Airport attack plot]]
* [[2009 Bronx terrorism plot]]
* [[2010 transatlantic aircraft bomb plot]]
* [[2023 Hamas-led attack on Israel]] ("7/10")
* [[2004 Madrid train bombings]] ("11M", abbr. of March 11)}}

== References ==
=== Notes ===
{{notelist}}

=== Citations ===
{{reflist}}

== Bibliography{{anchor|Sources}} ==
{{refbegin|30em}}
* {{cite report|chapter-url=http://www.9-11commission.gov/report/911Report_Ch1.pdf|title=''9/11 Commission Report''|chapter=Chapter 1.1: 'We Have Some Planes': Inside the Four Flights|year=2004|publisher=National Commission on Terrorist Attacks Upon the United States|access-date=March 18, 2016}}
* {{cite journal|title=Unity of Purpose/Unity of effort: Private-Sector Preparedness in Times of Terror |journal=Disaster Prevention & Management |last1=Alavosius |first1=Mark P. |last2=Rodriquez |first2=Nischal J. |year=2005 |volume=14 |doi=10.1108/09653560510634098 |issue=5|page=666 |bibcode=2005DisPM..14..666A }}
* {{cite web |url=https://www.ntsb.gov/about/Documents/AAL77_fdr.pdf |title=American Airlines Flight 77 FDR Report |publisher=National Transportation Safety Board |date=January 31, 2002 |access-date=September 3, 2011 }}
* {{cite report |last=Averill |first=Jason D. |url=http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201-7.pdf |archive-url=https://web.archive.org/web/20090509033658/http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201-7.pdf |archive-date=May 9, 2009 |title=Final Reports of the Federal Building and Fire Investigation of the World Trade Center Disaster |publisher=National Institute of Standards and Technology (NIST) |year=2005 |access-date=September 2, 2011 }}
* {{cite book|last=Bergen|first=Peter L.|title=Holy War, Inc.: Inside the Secret World of Osama Bin Laden|url=https://books.google.com/books?id=sRhZDrJb0zgC&pg=PP1|year=2001|publisher=Simon and Schuster|isbn=978-0-7432-3467-2|access-date=March 18, 2016}}
* {{cite book|last=Bergen|first=Peter|title=The Osama Bin Laden I Know: An Oral History of Al Qaeda's Leader|url=https://books.google.com/books?id=_XkM92XMlQ4C&pg=PP1|year=2006|publisher=Simon and Schuster|isbn=978-0-7432-9592-5|access-date=March 18, 2016}}
* {{cite book|first=Brad|last=Berner|title=The World According to Al Qaeda|url=https://books.google.com/books?id=smP3gFyQpXQC&pg=PP1|year=2007|publisher=Peacock Books|isbn=978-81-248-0114-7|access-date=March 18, 2016}}
* Bodnar, John.. ''Divided by Terror: American Patriotism after 9/11'' (University of North Carolina Press, 2021) how memory of the event stimulated and reshaped patriotism.
* {{cite book|last1=Clarke|first1=Richard|title=Against All Enemies: Inside America's War on Terror|year=2004|publisher=Free Press|location=New York|isbn=978-0-7432-6024-4|url=https://archive.org/details/againstallenemie00clar|url-access=registration}}
* {{cite book |last1=Dwyer |first1=Jim |last2=Flynn |first2=Kevin |title=102 Minutes |publisher=Times Books |year=2005 |url=https://books.google.com/books?id=-Ctk6LxDDR8C&pg=PP1 |isbn=978-0-8050-7682-0 |access-date=March 18, 2016 }}
* {{cite report |url=https://www.nist.gov/customcf/get_pdf.cfm?pub_id=861610 |title=Final Report on the Collapse of World Trade Center Building 7 |date=November 2008 |publisher=[[National Institute of Standards and Technology]] |access-date=April 11, 2012 |format=PDF |ref={{harvid|''Final Report on the Collapse of World Trade Center Building 7''|2008}} }}
* {{cite web |title=Flight Path Study – American Airlines Flight 77 |url=http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB196/doc02.pdf |date=February 19, 2002 |publisher=[[National Transportation Safety Board]] |access-date=September 3, 2011 }}
* {{cite book|last1=Fouda|first1=Yosri|last2=Fielding|first2=Nick|title=Masterminds of Terror: The Truth Behind the Most Devastating Terrorist Attack the World Has Ever Seen|url=https://books.google.com/books?id=IASlEi7rogIC&pg=PP1|year=2004|publisher=Arcade Publishing|isbn=978-1-55970-717-6|access-date=March 18, 2016}}
* {{cite book |last1=Goldberg |first1=Alfred |last2=Papadopoulos |first2=Sarandis |last3=Putney |first3=Diane |last4=Berlage |first4=Nancy |last5=Welch |first5=Rebecca |display-authors=1 |title=Pentagon 9/11 |url=https://books.google.com/books?id=wfhI5oc41sMC&pg=PP1 |year=2007 |publisher=Government Printing Office |location=Washington, D.C. |isbn=978-0-16-078328-9 |access-date=March 18, 2016 |ref={{harvid|Goldberg et al.|2007}} }}
* {{cite book |last=Graff |first=Garrett M. |author-link=Garrett Graff |year=2019 |title=The Only Plane in the Sky: An Oral History of 9/11 |url=https://books.google.com/books?id=we-oDwAAQBAJ&pg=PA5 |location=New York |publisher=Avid Reader Press |isbn=978-1-5011-8220-4 }}
* {{cite book|last=Gunaratna|first=Ronan|title=Inside Al Qaeda: global network of terror|url=https://archive.org/details/insidealqaedaglo00guna|url-access=registration|year=2002|publisher=Columbia University Press|isbn=978-0-231-12692-2}}
* {{cite book|last=Holmes|first=Stephen|title=Making sense of suicide missions|year=2006|publisher=Oxford University Press|chapter-url=https://books.google.com/books?id=eciSejVv-YoC&pg=PP1|isbn=978-0-19-929797-9|editor=Diego Gambetta|chapter=Al Qaeda, September 11, 2001|access-date=March 18, 2016}}
* {{cite book |title=The Al Qaeda reader |first1=Raymond |last1=Ibrahim |last2=bin Laden |first2=Osama |url=https://books.google.com/books?id=Ne5JZYf-dlkC&pg=PR2 |year=2007 |publisher=Random House Digital, Inc. |isbn=978-0-385-51655-6 |access-date=March 18, 2016 }}
* {{cite journal |last1=Javorsek II |first1=Daniel |last2=Rose |first2=John |last3=Marshall |first3=Christopher |last4=Leitner |first4=Peter |title=A Formal Risk-Effectiveness Analysis Proposal for the Compartmentalized Intelligence Security Structure |journal=International Journal of Intelligence and CounterIntelligence |date=August 5, 2015 |volume=28 |issue=4 |pages=734–61 |doi=10.1080/08850607.2015.1051830 |s2cid=152911592}}
* {{cite journal |last1=Jessee |first1=Devin |title=Tactical Means, Strategic Ends: Al Qaeda's Use of Denial and Deception |journal=International Journal of Intelligence and CounterIntelligence |year=2006 |volume=18 |issue=3 |pages=367–88 |doi=10.1080/09546550600751941 |s2cid=144349098 |url=http://web.international.ucla.edu/media/files/FTPV_A_175157_P.pdf |access-date=March 23, 2016 |archive-date=November 21, 2021 |archive-url=https://web.archive.org/web/20211121230603/https://web.international.ucla.edu/media/files/FTPV_A_175157_P.pdf |url-status=live}}
* {{cite book|first=Christopher|last=Kelley|title=Executing the Constitution: putting the president back into the Constitution|url=https://books.google.com/books?id=qgzmexCI734C&pg=PP1|year=2006|publisher=SUNY Press|isbn=978-0-7914-6727-5|access-date=March 18, 2016}}
* {{cite book |last1=Keppel |first1=Gilles |last2=Milelli |first2=Jean-Pierre |last3=Ghazaleh |first3=Pascale |title=Al Qaeda in its own words |url=https://archive.org/details/isbn_9780674028043 |url-access=registration |year=2008 |publisher=Harvard University Press |isbn=978-0-674-02804-3 |access-date=March 18, 2016 }}
* {{cite book |last=Lawrence |first=Bruce |title=Messages to the world: the statements of Osama Bin Laden |url=https://books.google.com/books?id=3_fRlEZoaioC&pg=PP1 |access-date=May 29, 2014 |year=2005 |publisher=Verso |isbn=978-1-84467-045-1 }}
* {{cite book|title=The SAGE Encyclopedia of Terrorism, Second Edition|first=Gus|last=Martin|url=https://books.google.com/books?id=I_jh4VBi_HYC&pg=PP1|year=2011|publisher=Sage|isbn=978-1-4129-8017-3|access-date=March 18, 2016}}
* {{cite book|last=McDermott|first=Terry|title=Perfect Soldiers: The 9/11 Hijackers|year=2005|publisher=HarperCollins|pages=191–192|url=https://books.google.com/books?id=4Oufo58esZAC&pg=PP1|isbn=978-0-06-058470-2}}
* {{cite web |url=http://home2.nyc.gov/html/fdny/html/mck_report/toc.shtml |archive-url=https://web.archive.org/web/20100603212555/http://home2.nyc.gov/html/fdny/html/mck_report/toc.shtml |url-status=dead |archive-date=June 3, 2010 |title=McKinsey Report |publisher=FDNY / McKinsey & Company |date=August 9, 2002 |access-date=September 25, 2011 }}
* {{cite book|title=The Israel Lobby and U.S. Foreign Policy|first=John J.|last=Mearsheimer|publisher=Macmillan|year=2007|isbn=978-0-374-17772-0|url=https://books.google.com/books?id=zIrFUBs7G6kC}}
* {{cite book|title=Osama Bin Laden|first=Suzanne|last=Murdico|url=https://books.google.com/books?id=SSHiERbJuKMC&pg=PP1|publisher=Rosen Publishing Group|year=2003|isbn=978-0-8239-4467-5}}
* {{cite web |url=http://www.fire.nist.gov/bfrlpubs/build03/PDF/b03017.pdf |archive-url=https://web.archive.org/web/20110721055255/http://www.fire.nist.gov/bfrlpubs/build03/PDF/b03017.pdf |archive-date=July 21, 2011 |title=The Pentagon Building Performance Report |publisher=American Society of Civil Engineers (ASCE) |date=January 2003 |access-date=September 3, 2011 }}
* {{cite book |last1=Summers |first1=Anthony |last2=Swan |first2=Robbyn |title=The Eleventh Day: The Full Story of 9/11 and Osama Bin Laden |year=2011 |publisher=Ballantine Books |location=New York |url=https://archive.org/details/eleventhdayfulls0000summ |url-access=registration |isbn=978-1-4000-6659-9 |access-date=March 18, 2016 }}
* {{cite book|last=Sunder|first=Shyam S. |title=Final Report on the Collapse of the World Trade Center Towers |id=NIST NCSTAR 1 |publisher=[[National Institute of Standards and Technology]] (NIST) |date=September 2005 |url=https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=909017 |access-date=September 11, 2024}}
* {{cite web |url=http://www.fema.gov/pdf/library/fema403_ch6.pdf |title=World Trade Center Building Performance Study – Bankers Trust Building |date=May 2002 |publisher=[[Federal Emergency Management Agency]] |access-date=July 12, 2007}}
* {{cite web |url=http://www.fema.gov/pdf/library/fema403_ch7.pdf |title=World Trade Center Building Performance Study – Peripheral Buildings |date=May 2002 |publisher=[[Federal Emergency Management Agency]] |access-date=September 3, 2011}}
* {{cite web|year=2002 |url=http://www.fema.gov/pdf/library/fema403_ch5.pdf|title=World Trade Center Building Performance Study |publisher=Federal Emergency Management Agency|access-date=September 2, 2011}}
* {{cite book |last=Wright |first=Lawrence |year=2006 |title=The Looming Tower: Al-Qaeda and the Road to 9/11 |publisher=Alfred A. Knopf |url=https://archive.org/details/loomingtoweralqa00wrig |url-access=registration |isbn=978-0-375-41486-2 |author-link=Lawrence Wright |location=New York |oclc=64592193}}
* {{cite journal |last1=Yitzhak|first1=Ronen |title=The War Against Terrorism and For Stability of the Hashemite Regime: Jordanian Intelligence Challenges in the 21st Century |journal=International Journal of Intelligence and CounterIntelligence|date=Summer 2016 |volume=29|issue=2|pages=213–35 |doi=10.1080/08850607.2016.1121038 |s2cid=155138286}}
{{refend}}

== Further reading ==
{{refbegin|30em}}
* {{cite book|publisher=National Commission on Terrorist Attacks|title=The ''9/11 Commission Report: Final Report of the National Commission on Terrorist Attacks Upon the United States''|url=https://books.google.com/books?id=TjKODEaahVQC&pg=PP1|date=July 30, 2010|isbn=978-1-61640-219-8}}
* {{cite book|first=Stephen E|last=Atkins|title=The 9/11 Encyclopedia|url=https://books.google.com/books?id=PDDIgWRN_HQC&pg=PP1|year=2011|publisher=ABC-CLIO|isbn=978-1-59884-921-9}}
* {{cite book |last=Bolton |first=M. Kent |year=2006|title=U.S. National Security and Foreign Policymaking After 9/11: Present at the Re-creation |url=https://books.google.com/books?id=IETboc9ajpQC&pg=PP1 |publisher=Rowman & Littlefield |isbn=978-0-7425-5900-4}}
* {{cite book |last=Caraley |first=Demetrios |author-link=Demetrios James Caraley |year=2002 |title=September 11, terrorist attacks, and U.S. foreign policy|url=https://books.google.com/books?id=xMCGStzPzooC&pg=PP1 |publisher=Academy of Political Science|isbn=978-1-884853-01-2}}
* {{cite book |last=Chernick |first=Howard |year=2005 |title=Resilient city: the economic impact of 9/11
|url=https://books.google.com/books?id=GL6vOpKbFygC&pg=PP1 |publisher=Russell Sage Foundation|isbn=978-0-87154-170-3}}
* {{cite book |last1=Damico |first1=Amy M |last2=Quay |first2=Sara E. |year=2010 |title=September 11 in Popular Culture: A Guide |url=https://books.google.com/books?id=mgtSLkKxIpEC&pg=PP1 |publisher=Greenwood |isbn=978-0-313-35505-9}}
* {{cite book |last=Hampton |first=Wilborn |year=2003 |title=September 11, 2001: attack on New York City|url=https://archive.org/details/september112001a00wilb|url-access=registration |publisher=Candlewick Press|isbn=978-0-7636-1949-7}}
* {{cite book |last=Langley |first=Andrew |year=2006 |title=September 11: Attack on America
|url=https://archive.org/details/september11attac0000lang|url-access=registration |publisher=Compass Point Books |isbn=978-0-7565-1620-8}}
* {{cite book |last1=Neria |first1=Yuval |author-link1=Yuval Neria |last2=Gross |first2=Raz |last3=Marshall |first3=Randall D. |last4=Susser |first4=Ezra S. |year=2006 |title=9/11: mental health in the wake of terrorist attacks|url=https://books.google.com/books?id=kADL4ymHsY8C&pg=PP1 |publisher=Cambridge University Press |isbn=978-0-521-83191-8}}
* {{cite book |last=Ryan |first=Allan A. |title=The 9/11 Terror Cases: Constitutional Challenges in the War against Al Qaeda |publisher=University Press of Kansas |year=2015|isbn=978-0-7006-2132-3}}
* {{cite book|first1=Steven |last1=Strasser |first2=Craig R |last2=Whitney |first3=National Commission on Terrorist Attacks upon the United States|last3=United States. Congress. Senate. Select Committee on Intelligence|title=The 9/11 investigations: staff reports of the 9/11 Commission: excerpts from the House-Senate joint inquiry report on 9/11: testimony from fourteen key witnesses, including Richard Clarke, George Tenet, and Condoleezza Rice|url=https://books.google.com/books?id=qLCn_D7lX5kC&pg=PP1|year=2004|publisher=PublicAffairs|isbn=978-1-58648-279-4}}
{{refend}}

==External links==
{{Prone to spam|date=August 2020}}<!-- PLEASE see [[Wikipedia:External links]] and [[Wikipedia:Spm]. -->
{{Sister project links|d=y|n=Category:9/11|q=September 11 attacks|c=Category:September 11 attacks|wikt=9/11|v=no|s=Category:September 11th attacks|b=no}}
* [https://www.9-11commission.gov/ National Commission on Terrorist Attacks Upon the United States] ''official commission website''
* [https://www.911memorial.org/visit/memorial/names-911-memorial/ List of victims]
* [https://memory.loc.gov/ammem/collections/911_archive/ September 11, 2001, Documentary Project] from the U.S. [[Library of Congress]], ''Memory.loc.gov''
* [https://lcweb2.loc.gov/diglib/lcwa/html/sept11/sept11-overview.html September 11, 2001, Web Archive] from the U.S. [[Library of Congress]], ''Minerva''
* [https://www.gwu.edu/~nsarchiv/NSAEBB/sept11/index.html National Security Archive]
* [https://911digitalarchive.org/ September 11 Digital Archive: Saving the Histories of September 11, 2001], from the ''Center for History and New Media'' and the ''American Social History Project/Center for Media and Learning''
* [[s:Verbatim Transcript of Combatant Status Review Tribunal Hearing for ISN 10024|DoD: Khalid Sheikh Mohammed Verbatim Transcript of Combatant Status Review Tribunal Hearing for ISN 10024]], from Wikisource
*[https://911legacies.com/ The 9/11 Legacies Project], ''Oriental Institute, Czech Academy of Sciences, Prague''
*[https://responsiblestatecraft.org/tag/911at20/ 9/11 at 20: A Week of Reflection], ''Responsible Statecraft, The Quincy Institute''
*[https://learninglab.si.edu/collections/subject-september-11-2001-related-photography-nmahphc/3T8uqT3trKhRappW September 11, 2001 collection] at the [[National Museum of American History|Smithsonian National Museum of American History]]

{{Spoken Wikipedia|En-September-11-attacks.ogg|date=September 11, 2019}}

'''Multimedia'''
<!-- ATTENTION! DO ''NOT'' ADD LINKS WITHOUT DISCUSSION AND CONSENSUS ON THE TALK PAGE. -->
* [https://www.cnn.com/SPECIALS/2001/trade.center/multimedia.day.html Day of Terror Video Archive] – CNN.com

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