But before the MH17 crash, security concerns closed Ukrainian airspace. An airliner flies under smoke left by a Ukrainian military plane a few kilometres from the Russian border on July 16. Credit:AFP The US Federal Aviation Administration issued a "special notice" regarding Ukrainian airspace advising airlines to "exercise extreme caution due to the continuing potential for instability" and Eurocontrol warned pilots and airlines to avoid Ukrainian airspace due to serious risks. Aviation experts last night said operators continued to fly across the zone because it was the quickest and cheapest route for some flights. Brian Flynn, a spokesman for Eurocontrol, which directs air traffic across Europe, said Ukrainian aviation authorities had closed the airspace below 32,000 feet on Monday after having earlier restricted the airspace below 26,000 feet, on July 1. In both cases, the closures came as a result of security concerns after rebels shot down Ukrainian military aircraft.

Mr Flynn said it is up to the Ukrainian government to decide whether and how to restrict airspace, with Eurocontrol responsible for helping to implement those decisions. The plane crash site near the settlement of Grabovo. Credit:Reuters Before the crash, 300 commercial aircraft a day were flying through eastern Ukrainian airspace, with most serving as long-haul flights between Europe and Southeast Asia. Mr Flynn said such flights typically cruise at between 33,000 and 37,000 feet. Qantas said on Friday it had shifted the flight path for its London to Dubai route over Ukraine some 400 nautical miles to the south several months ago. A Qantas spokesman declined to comment on the reasons for the shift, which came amid heightened tensions between Kiev and pro-Moscow rebels.

Mr Flynn said airlines can elect to avoid an area even if it’s not closed, but that he did not believe any had chosen to do so in eastern Ukraine. “I’m not aware of any airlines that were specifically avoiding that area,” he said. Norman Shanks, a former head of group security at airports group BAA, said: "Malaysia Airlines, like a number of other carriers, has been continuing to use it because it is a shorter route, which means less fuel and therefore less money. Attacks on aircraft in the area have been rife. In the past week alone two Ukrainian military aircraft were shot down and a third was damaged by a missile." Immediately after the crash yesterday, several other airliners followed the same path and did not re-route, including Singapore Airlines and Kazakhstan Airlines. Etihad and Emirates were also originally reported as taking the same route, but both airlines later confirmed they did not operate in Ukrainian airspace. On Thursday night a British Department for Transport spokesman confirmed that flights, including those already airborne, were being routed around the region.

Virgin Atlantic said it had diverted a small number of flights, believed to include routes from Heathrow to Dubai and one on the Mumbai to Heathrow route. Turkish Airlines said all of its flights would now avoid Ukrainian airspace. British Airways said only one flight a day used that airspace, the Heathrow to Kiev service. A spokesman said: "The safety and security of our customers is always our top priority. "We are keeping those services under review, but Kiev is several hundred kilometres from the incident site." Other operators that were diverting flights over Ukraine on Thursday night were Italy's Alitalia, Lufthansa, Air France and the Russian carriers Aeroflot, and Transaero. It is understood airliners continued to cross volatile regions because operators believed they were at a sufficient altitude not to be at risk of attack. It was for this reason that commercial airliners continued to fly over Iraq and Afghanistan during prior conflicts, although it has been reported that the US Federal Aviation Administration has recently told carriers to avoid the Crimea.

The Malaysian Airlines flight was reportedly travelling at an altitude of about 33,000 feet - an altitude considered by those within the industry to be completely safe. Military jets typically fly at much lower altitudes, meaning it would be hard to misinterpret an airliner at such height as a threat, and many ground-based weapons would not reach such an altitude. On Monday a Ukrainian military transport plane carrying eight people was hit by a missile fired from Russian territory killing two of those on board. On Wednesday a Ukrainian Air Force Su-25 fighter was also hit by a missile, forcing the pilot to eject. Earlier that day another Su-25 was hit by a rebel missile but the pilot landed the plane successfully with relatively slight damage. An industry source said: "The belief was that a plane could not be shot down at that altitude, which is why aircraft continue to fly over zones that have wars going on."

Loading David Kaminski-Morrow, the air transport editor of Flightglobal magazine, added: "Any decision about the opening or closing of Ukrainian airspace will be a matter for the Ukrainians. It could well be that all of that airspace will now be closed." The Daily Telegraph, London, with Washington Post and Reuters