The pilot of the Air France jet which plunged into the Atlantic in 2009 killing 228 people, pushed the nose upward instead of downward during a stall because of false data from sensors, the father of a victim says.
Robert Soulas was briefed by French air accident investigators today about their final report into the Airbus A330 crash.
He says investigators said the flight director system indicated "erroneous information" that the plane was diving downward, "and therefore to compensate, the pilot had a tendency to pull on the throttle to make it rise up".
Investigators had known the pilot nosed upward during the stall instead of down, which would have been the normal manoeuvre for stall recovery. But they did not know why.
Mr Soulas' comments are the first indication of why the pilot made that decision.
The full report is due to be released later today.
France's BEA air accident investigation agency has spent three years digging into what caused the frenetic end of Flight 447. The plane flying from Rio de Janeiro to Paris plunged into the ocean during a night-time thunderstorm, in Air France's deadliest ever crash.
The report is also expected to expand on why the pilot nosed upward at such a sharp angle, and why the two co-pilots in the cockpit at the time appeared to ignore dozens of stall warnings going off in the four and a half before the plane slammed into the ocean.
Barbara Crolow, a German who lost her son in the crash, said she was "disappointed" because she felt the report focuses too much on pilot error.
"I think this is not enough. ... There have been other reasons as well and they ignored them," she said.
Pilot Gerard Arnoux defended the pilots' actions, saying they were doing what they had been taught to do. "A normal pilot on a normal airliner follows" the signals on the flight director system, which tells them to go left, right, up or down, he said.
He noted that a European directive last year modified procedures to tell pilots to ignore the signals if they lose data on the plane's speed.
A preliminary report released last July described a confused Air France cockpit crew getting incoherent speed readings from faulty sensors, but it did not draw a conclusion on what caused the crash.
The BEA's findings raised worrisome questions about the reactions of the two co-pilots as the A330 went into an aerodynamic stall, and their ability to fly manually as the autopilot disengaged. Broader concerns were raised about training for pilots flying high-tech planes when confronted with a high-altitude crisis.
The report included a study of the plane's black box flight recorders, uncovered in a costly and extraordinarily complex search in the ocean depths.
In a separate French judicial investigation still under way, Air France and Airbus have been handed preliminary manslaughter charges.