Ukraine said early on Thursday it had restricted civilian flights in its airspace due to "potential hazard", hours after a conflict zone monitor warned airlines should stop overflights over the risk of an unintended shootdown or cyber attack.
The notice to airmen from Ukraine's authorities, issued at 0156 GMT on Thursday, is due to expire at 2359 GMT unless extended. It did not specify whether the restriction was a total ban on civilian flights but Eurocontrol, which coordinates air traffic in Europe, said that Ukraine's airspace was not available because of military restrictions.
An El Al flight from Tel Aviv to Toronto made a sudden U-turn out of Ukraine's airspace around the time a notice to airmen was issued citing the restrictions, according to flight tracking website FlightRadar24.
A LOT Polish Airlines flight from Warsaw to Kyiv also turned back to Warsaw around the same time.
The turnarounds came after Safe Airspace, which was set up to provide safety and conflict zone information for airlines after Malaysia Airlines flight MH17 was shot down over eastern Ukraine in 2014, said it had increased its risk level to "do not fly".
"Regardless of the actual movements of Russian forces into Ukraine, the level of tension and uncertainty in Ukraine is now extreme," Safe Airspace said on its website. "This itself gives rise to significant risk to civil aviation."
It also warned of the potential for a cyberattack on Ukraine's air traffic control.
Separatists in Ukraine asked on Wednesday for Russian help to repel "aggression" and Kyiv announced compulsory military service and a state of emergency as the West slapped more sanctions on Moscow in a bid to stop an all-out invasion.
Russia has closed some airspace in the Rostov flight information region to the east of its border with Ukraine "in order to provide safety" for civil aviation flights, according to a notice to airmen.
Before Ukraine advised of the airspace restrictions, the United States, Italy, Canada, France and Britain had told their airlines to avoid certain airspace above eastern Ukraine and Crimea but stopped short of a total ban.
The US Federal Aviation Administration said in its latest guidance on February 9 that a cross-border conflict between Ukraine and Russia could pose a direct or indirect threat to civil aviation.
Germany's Lufthansa halted flights to Ukraine from Monday, joining KLM which already suspended flights.
Two Ukrainian airlines last week disclosed problems in securing insurance for some of their flights while foreign carriers began avoiding the country's airspace as Russia massed a huge military force on its border.
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