The chances of recovering the black boxes of the Air France jet that crashed into the Atlantic last week are slim, the carrier's head, Pierre-Henri Gourgeon said in Paris on Thursday.
"It would be quite an accomplishment if the flight data recorders were recovered," Gourgeon told journalists, adding that the devices had never before been recovered from such ocean depths as is being attempted.
Reports say the plane wreckage may be more than 4,800 metres deep. By comparison, in 2007 the black box of a Boeing 737 that crashed off Indonesia was recovered at a depth of about 1,500 metres.
Investigators into the crash consider the black boxes, a cockpit voice recorder and a flight data recorder, essential to finding the cause of the accident, which killed 228 people.
But much will also be learned about the circumstances of the crash from the autopsies of the victims, Gourgeon said.
"We will know a great deal more when the autopsies clarify the technical reason of their deaths, if I can put it that way," he said.
The fragments from the airplane will also yield important information about what caused the Airbus A330-200 to plunge into the sea in the early hours of June 1 while flying from Rio de Janeiro to Paris.
Investigators and French media have seized on the malfunction of the aircraft's airspeed sensors, known as Pitot tubes, as a possible reason for the disaster.
But Gourgeon said he was "not convinced that the sensors are the reason for the crash."
Blocked or frozen Pitot tubes can lead to contradictory airspeed indications, preventing pilots from taking correct decisions. The doomed aircraft sent such inconsistent speed readings in the final minutes of its flight.