Flights above Ukraine were cancelled as the Russian invasion began, with many neighbouring countries also closing their airspace.
Commercial planes were grounded as Vladimir Putin began his missile assault in the early hours of the morning, leaving airports in the country abandoned.
Ukraine’s infrastructure ministry announced all air traffic was being halted shortly after midnight.
An El Al flight from Tel Aviv to Toronto made a sudden U-turn out of Ukraine’s airspace around the time of its closure, flight tracking website FlightRadar24 showed.
A LOT Polish Airlines flight from Warsaw to Kyiv also turned back to Warsaw around the same time.
Neighbouring Moldova is diverting flights to airports elsewhere while Russia’s close ally Belarus also closed part of its airspace.
Flight maps appeared to show planes avoiding large parts of Russia itself with traffic concentrating on flying over eastern Europe and Turkey.
The European Union Aviation Safety Agency urgently told air operators of a high risk to civilian aircraft over Ukraine as it is now ‘an active conflict zone.’
It also warned airspace in Russia and Belarus within 100 nautical miles of their borders with Ukraine could pose safety risks.
‘In particular, there is a risk of both intentional targeting and misidentification of civil aircraft,’ the agency said in a conflict zone bulletin.
‘The presence and possible use of a wide range of ground and airborne warfare systems poses a high risk for civil flights operating at all altitudes and flight levels.’
In the UK, the Civil Aviation Authority confirmed it had instructed airlines to avoid Ukrainian airspace until further notice.
Aspokesman said: ‘At the request of the Department for Transport, we can confirm that we have issued a notice to UK airlines (Notam), instructing them to avoid Ukrainian airspace until further notice.’
In response several airlines including Ryanair cancelled planned services.
Many had been flying people in and out of Ukraine until yesterday as various countries told their citizens to leave.
In a statement, Ryanair said flights were suspended for ‘at least the next 14 days’ and has removed them from sale for ‘at least the next four weeks until further information becomes available from EU safety agencies’.
It added: ‘Ryanair remains committed to our services to/from Ukraine and we look forward to restoring flight services there as soon as it is safe to do so.
‘We sincerely regret and apologise for these unprecedented disruptions and any inconvenience that they will inevitably cause to our Ukrainian customers.’
Wizz Air cancelled its flights between Luton Airport and the Ukrainian cities of Kyiv and Lviv on Thursday.
The lack of flights will make it harder for British nationals to evacuate from Ukraine to the UK.
On Tuesday, Foreign Secretary Liz Truss urged Britons in the country to ‘leave now via commercial routes while they are still available’.
After the invasion began, the Foreign Office updated its travel advice to state: ‘Ukraine’s airspace is closed. It is likely that commercial routes out of Ukraine will be severely disrupted and roads across Ukraine could be closed.’
It added: ‘Russia’s military action in Ukraine will severely affect the British Government’s ability to provide consular assistance in Ukraine.
‘British nationals should not expect increased consular support or help with evacuating in these circumstances.’
Flights are continuing to operate over Russia, which is a route used by many services between the UK and Asia.
But Russia itself said on Thursday it had suspended domestic flights to and from several airports near its border with Ukraine.
In July 2014, Malaysian Airlines flight MH17 was shot down by a missile launched from an area of Ukraine controlled by pro-Russia separatists, killing all 298 people on board.
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