Finland's national airline Finnair has announced the suspension of flights over Ukrainian airspace, following Russia's launching of a military attack on Ukraine on Thursday morning.
The company does not currently fly directly to Ukraine, but Finnair does fly over the western part of the country on three routes - to Gazipasa in Turkey, Tel Aviv in Israel and Dubai in the United Arab Emirates.
These flights will now circumvent Ukrainian and Belorussian airspace until further notice.
The changes will have little effect on flight time, extending each route's duration by about 5-10 minutes.
Finnair's announcement comes as the European Union Aviation Safety Agency (EASA) issued a warning overnight about flying over the region due to the escalating political and military tensions, adding that there is a risk passenger planes could be inadvertently shot down.
"As a precautionary measure, operators should exercise extreme caution and avoid using the airspace within 100NM [nautical miles] of the Belorussian and Russia-Ukraine border," the agency said.
EASA added that Russia has also blocked part of Rostov's airspace on the eastern Ukrainian border, with the Russian Ministry of Defense issuing a warning to Ukraine at 00.45 local time about the high risk to aviation safety.
This, in effect, called for the cessation of flights to civilian aircraft, EASA added.
Following this warning, regional air traffic control in Ukraine began turning aircraft back. An El Al Israel Airlines to Toronto was turned back to Tel Aviv upon entering the airspace.
Eurocontrol, which monitors European airspace, has also warned airlines of the dangers of flying over the region. The organisation's Director General Eamonn Brennan tweeted early on Thursday morning that flights to Ukraine have been suspended.
In addition to direct military action, there is an added risk of possible cyber attacks on Ukrainian air traffic control systems.
According to flight monitoring sites, airlines are now circulating the airspace of Belarus and Ukraine. In practice, the country's airspace should now contain no civilian aircraft.