``It is very rare for aviation accidents to have one single cause,'' according to a civil aviation authority spokesman. ``Look at any disaster -- unless it's caused by a terrorist bomb, it's normally down to a number of factors which, taken individually, would not cause a major problem.''

However, experts pointed out that EgyptAir 990 vanished without warning from the radar screens yesterday and no mayday signal was sent -- suggesting that the jet fell out of the sky as a result of a single catastrophic event.

The airline was quickly to say that it had received no terrorist threats. Earlier this month, a man hijacked an EgyptAir jet on its way from Istanbul to Cairo. He finally surrendered topolice in Germany.

Another more controversial theory being touted yesterday was that flight 990 was a victim of ``the Bermuda Triangle of the north''. The crash, in the North Atlantic off Nantucket, Massachusetts, is the fourth air accident to occur in the area in nearly as many years.