Ukrainian authorities have closed the airspace in the east of the country to all airline flights, the European flight safety body, Eurocontrol, has announced.
Eurocontrol said all flight plans that use routes in the area are being rejected.
It follows the crash of Malaysia Airlines flight MH17 with 295 people on board, amid claims it was shot down.
Flights already airborne are being routed around the area by air traffic control in the region, a Department for Transport spokesperson said.
Flight MH17 was on a flight from Amsterdam to Kuala Lumpur when it came down near the village of Grabovo.
The European Cockpit Association (ECA), which represents more than 38,000 European pilots, said the route flown by the crashed Malaysian aircraft was “the most common route for flights from Europe to South East Asia”.
Airline Emirates said its flight EK171 from Dubai to Kiev had returned to Dubai “due to the safety concerns raised with the latest reports on Malaysian flight MH17”.
It added that its flights to Kiev were suspended “with immediate effect, till further notice”.
Emirates said its flights to and from the US and other European destinations used a different route and were outside the zone where the incident involving MH17 occurred.
Lufthansa said it had decided to “fly a wide detour around east Ukrainian airspace with immediate effect”.
The airline said the decision would affect four of its flights on Thursday.
Similarly, Virgin Atlantic said it would re-route “a small number” of its flights on Thursday, following the incident.
British Airways said its flights did not use Ukrainian airspace, with the exception of a once-a-day service between Heathrow and Kiev.
A spokesman for BA said they were keeping those services under review, but that “Kiev is several hundred kilometres from the incident site”.
Abu Dhabi based Etihad said it was unaffected as its planes didn’t fly over the space.
KLM said that as a precautionary measure it already avoided flying over the concerned territory.
And Russian airline Aeroflot said its London to Moscow flights would experience a delay of 30 to 40 minutes on Thursday.
Turkish Airlines has said all of its flights would avoid Ukrainian airspace, while Italy’s Alitalia and Air France said they would divert their flights away from eastern Ukrainian airspace.
France’s junior transport minister Frederic Cuvillier said he had told “French airlines to avoid Ukraine’s air space as long as the reasons behind this catastrophe are not known.”
Flight MH17 had been due to enter Russian airspace when contact was lost.
Both the Ukrainian government and rebels have denied shooting it down in the region close to the Russian border.
Eurocontrol said the aircraft had been flying at Flight Level 330 (approximately 33,000 feet) when it disappeared from the radar.
This route had been closed by the Ukrainian authorities from ground to flight level 320 but had been open at the height level at which the aircraft was flying.
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