F-GZCP, the Air France jet which crashed, is seen here in an undated image The Air France jet which crashed into the Atlantic en route from Rio in 2009 stalled and fell in three and a half minutes, French investigators report.
The air accident investigations bureau (BEA) found the crew had struggled with contradictory speed readings just before the plane crashed.
A principal theory for the cause of the crash is that the jet’s speed probes iced up, resulting in faulty data.
All 228 people on board were killed in the disaster.
The BEA findings were released in an online statement in response to speculation in the media over the findings from the flight recorders, only recovered from the sea this month.
A full report into the disaster is not expected until next year.
Airbus, the maker of the A330 jet involved, said the French statement was a “significant step” in understanding the causes of the crash.
Ahead of Friday’s statement, the BEA said it wished to correct “partial and more or less contradictory information published in the media”.
It was giving “factual elements on the operation of the flight that… establish the circumstances of the accident but not the causes”.
According to the statement, the twin-engine jet’s autopilot and auto-thrust disengaged after it ran into turbulence, and the plane slowed dangerously, climbing to 38,000 ft (9,100m).
Speeds displayed on the left primary flight display were inconsistent with those on the integrated standby instrument system.
French investigators have been working on the theory that the speed sensors, known as Pitot probes, malfunctioned because of ice at high altitude.
This may have set off an unpredictable chain of events.
The flight recorders were displayed to the public before being decoded The drama began while the captain was taking a routine rest, with the two co-pilots in the cockpit, the BEA said.
Summoned to help, however, he was back in the cockpit two minutes and 48 seconds before the crash, it found.
The BEA statement found the composition of the crew had been “in accordance with the operator’s procedures”.
Flight AF 447 went down on 1 June 2009 after running into an intense high-altitude thunderstorm, four hours into a flight from Rio de Janeiro in Brazil to Paris.
Those on board came from more than 30 countries, though most were French, Brazilian or German.
The wreckage of the plane was discovered after a long search of 10,000 sq km (3,860 sq miles) of sea floor.
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