Ukraine said on Thursday it had closed its airspace to civilian flights because of a "high risk" to safety, and Europe's aviation regulator also warned about the hazards of flying in bordering areas of Russia and Belarus because of military activities.
Russian President Vladimir Putin authorized a military operation in eastern Ukraine on Thursday in what appeared to be the start of the war in Europe.
Ukraine State Air Traffic Services Enterprise said on its website that the country's airspace was closed to civilian flights starting at 0045 GMT on Thursday and that air traffic services had been suspended.