Experts have yet to come to a definitive conclusion as to what caused the crash that killed 224 people.

“We absolutely exclude the technical failure of the plane, and we absolutely exclude pilot error or a human factor,” Aleksandr Smirnov, the airline’s deputy director for aviation said.

There have been unsubstantiated claims by Islamic State that they brought down the jet and others have suggested that it could have been a bomb.

Professor Michael Clarke, director general of the Royal United Services Institute, suggested that a bomb may have caused the crash.

"There’s no sign of a distress call, so the idea that the aircraft was undergoing an mechanical problem, or an engine problem, or a fire, or something like that, you would expect that there would be some sort of distress call beforehand," he told BBC Radio Five Live.

"So the fact that there was a catastrophic failure at 31,000 feet, with the aircraft falling in two pieces, suggests to me an explosion on board.

"So was this caused by some form of terrible accident, which is unlikely, or a bomb, which is much more likely, my mind is moving in that direction rather than anything that happened on the ground."

The Airbus A321 was operated by Kogalymavia. It came down over the Sinai peninsula 23 minutes after it took off from the resort of Sharm el-Sheikh en route to the Russian city of St Petersburg.