Crash investigators say the pilots of an Air France jet struggled for 3.5 minutes to regain control of their plane before it plunged into the Atlantic Ocean two years ago.
All 228 people on board were killed when the aircraft crashed during a flight from Rio de Janeiro to Paris on 1 June, 2009.
Flight recorders from the plane were recovered from the sea earlier this month.
A preliminary statement has been issued by the Bureau of Investigation and Analysis in France.
The BBC reports that one of the instruments showed ''a sharp fall'' in air speed as the plane entered a high-altitude thunderstorm, four hours into the flight.
The stall warning sounded and the autopilot and auto-thrust disengaged.
As the plane slowed, it climbed to 38,000 ft (11,600m).
For a period of almost a minute, speeds displayed on the left primary flight display were inconsistent with those on the integrated standby instrument system.
The statement did not look at the causes of the crash. A full report into the disaster is not expected until next year.
Air France said on Friday that it appeared ''the initial problem was the failure of the speed probes''.