With two co-pilots at the helm, Air France Flight 447 went down into the Atlantic two years ago after speed sensors failed and the Airbus jet stalled, a German newspaper reported.
Der Spiegel cited sources who are familiar with the contents of flight recorders recovered from the ocean two weeks ago. The unnamed sources told the newspaper that the chief pilot, Captain Marc Dubois, had left the cockpit just before the Airbus A330's airspeed sensors failed four hours into the flight. The failure of the sensors caused the autopilot to disengage and the plane to stall, going into an uncontrolled dive.
The air speed sensors have long been suspected as the cause of the crash. Air France flight 447 was en route from Rio de Janeiro to Paris May 31, 2009, when it when down in the Atlantic Ocean, killing all 228 people aboard.
Its last known communication was about four hours into the flight.
Before the crash, the pilot had sent an electronic text message to the airline to say that the plane was heading to an area known for stormy weather; Intertropical Convergence Zone.
About 24 automated messages during four minutes were sent from the plane before it disappeared from radar. The messages recorded system failures and variable speed readings.
A team from Woods Hole Oceanographic Institution discovered the plane's wreckage last month using remote underwater submarines about 2.5 miles deep.
"Overall feelings were bittersweet. We were happy we had found it, and a little sad that we were witnessing this tragedy," said Mike Purcell, senior research engineer at Woods Hole Oceanographic Institution.
Of those who died, 51 bodies have been found but 177 are still missing.
Since the crash, several theories have emerged on what brought down the jet liner including problems with the plane's speed sensors called pitot tubes - which officials believe may have malfunctioned. Now it appears that it was indeed the tubes that caused the crash, though the exact cause has not been announced.
France's BEA air-accident investigation bureau has not yet commented on the findings of the flight recorders. The agency said it will make a statement on May 27.
Der Spiegel reported that the black boxes showed the Air France plane climbed sharply after the speed-sensor failure and Captain Dubois returned to the cockpit shortly before the crash. From another part of the plane, the caption had communicated with the cockpit on actions to save the aircraft, the newspaper said.
The pitot tubes had been known to fail after becoming clogged with ice. Air speed is critical to a plane's stability -- there is a very narrow band of speed in which the plane can operate safely at high altitudes.
ABC News' Lisa Stark, Cindy E. Rodriguez, Christophe Schpoliansky and the Associated Press contributed to this report.