A research analyst at the professional forum the Royal United Services Institute said it was possible that the Malaysia Airlines plane could have been brought down by a surface-to-air missile, which he believed would have been flying at 33,000 feet.
Justin Bronk said: "Unfortunately it is possible.
"There have been unconfirmed reports in the past few days of a system called SA-11, which Russia names 'Buk'. It has been seen around Donetsk, and that is a much heavier system. It looks like a tank with four large missiles on top and it is capable of shooting down an airliner at that sort of altitude."