The crew piloting a doomed Air France jet over the Atlantic did not appear to know that the plane was in a stall, despite repeated warning signals, and never informed the passengers that anything was wrong before the jet plunged into the sea, according to new findings released Friday.

Based on cockpit recordings from the crash, the French air accident investigation agency is recommending mandatory training for all pilots to help them fly planes manually and handle a high-altitude stall.

All 228 people were killed when the Airbus 330, route from Rio de Janeiro to Paris, crashed amid thunderstorms over the Atlantic on June 1, 2009. It was the worst accident in Air France's history.

The passengers were never told what was happening as Flight 447 went into an aerodynamic stall and then dived for 3½ minutes into the sea, according to a summary of the latest findings released Friday by the BEA — France's civil aviation safety authority.

The pilots themselves may not have been aware they were in the stall even as it was dooming the flight, the summary says.

The BEA will release the full report later Friday, based on cockpit voice and data recorders retrieved from the ocean depths in May in an exceptionally long and costly search operation.

Sensors obstructed

The summary confirms that external speed sensors obstructed by ice crystals produced irregular speed readings on the plane. Since the accident, Air France has replaced the speed monitors on all its Airbus A330 and A340 aircraft.

The BEA says neither of the co-pilots at the controls had received recent training for manual aircraft handling or had any high-altitude schooling in case of unreliable air speed readings.

A stall warning sounded numerous times, and once for a full 54 seconds, but the crew made no reference to it in cockpit exchanges before the jet crashed, according to the BEA.

There was no evidence of task-sharing during the crisis by the two co-pilots in the cockpit at the time, according to the BEA's findings. The captain was on a rest break when the warnings began.

The BEA says it's unclear why the co-pilot at the controls, flying manually in what became the final minutes of the flight, maintained a nose-up input — contrary to the normal procedure to come out of an aerodynamic stall. Normally, the nose should be pointed slightly downward to regain lift in such a stall, often caused because the plane is traveling too slowly.

This is the most extensive report by investigators to date. A final report is expected at a later date.