Aviation experts fear the cause of the Air France plane crash in the Atlantic with the loss of 228 lives may never be known.
French air accident investigators will tomorrow publish the first official report into the June 1 accident involving an Airbus A330 aircraft flying from Rio de Janeiro to Paris.
But with hopes of finding the plane's "black box" flight recorders all but gone, it is unlikely that investigators will be able to pinpoint the cause of the crash.
"We are a very long way from finding out exactly what went wrong with this flight," said Kieran Daly, editor of internet news service Air Transport Intelligence.
He went on: "It may be that we'll never know what happened to this plane. Then you would have a situation where a state-of-the-art aircraft has been lost in the middle of a flight for no known reason and that's very, very worrying."
Mr Daly said it was possible that crash investigators may be able to glean "something additional" from the automatic messages sent from the plane in the moments before all contact was lost.
But he added: "These messages have been in the public domain for some time and nobody has been able to come up with any firm conclusions.
"It's possible that the first report may be able to draw some conclusions from the debris recovered and the state of the bodies.
"We know the aircraft flew some distance into extremely bad weather but it is difficult to understand why it went as far into the bad weather as it appears to have done."
There has been speculation that the airspeed indication equipment - known as Pitot tubes - could have been faulty.
Mr Daly said: "There has been a history of problems with Pitot tubes on A330s. Getting wrong information on speed is quite a serious thing to happen and the problem is not necessarily immediately obvious to the flight crew."
Five Britons and three Irish nationals were among the dead on flight AF447.
Many of the lost passengers were French and today France was continuing to mourn the loss of more of its citizens in another Airbus crash.
A Yemenia Yemen Airways Airbus A310 went down in the Indian Ocean yesterday on a flight from Yemen to the Comoros islands.
A 14-year-old girl survived the accident to the plane which was carrying 153 people.Reuse content