PARIS - Confronted with faulty instrument readings and alarms going off in the cockpit, the pilots of an Air France jetliner struggled to tame the aircraft as it went into an aerodynamic stall, rolled, climbed, and finally plunged 38,000 feet into the Atlantic Ocean in just 31/2 minutes.

But the passengers on that doomed Rio de Janeiro-to-Paris flight were probably asleep or nodding off and didn't realize what was going on as the aircraft plummeted nose-up toward the ocean, the director of the French accident investigating bureau said after releasing preliminary data from flight recordings that provide new insight into the June 1, 2009, disaster.

All 228 people aboard the Airbus A330 died.

The brief, highly technical report by the BEA contains only selective remarks from the cockpit recorder, offers no analysis, and assigns no blame. It also does not answer the key question: What caused the crash?

Several experts familiar with the report said the copilot at the controls, at 32 the youngest of the three-man cockpit crew, Cedric Bonin, may have responded incorrectly to the emergency by pointing the nose upward, perhaps because he was confused by the incorrect readings.

The plane's external speed sensors, called Pitot tubes, have long been considered a likely culprit in the disaster, with experts suggesting they may have been iced over. And the BEA investigators found that two sets of instruments on the plane gave different speed readings, with the discrepancies lasting less than a minute.

Since the accident, Air France has replaced the speed monitors on all its Airbus A330 and A340 aircraft.

An official at Airbus said the aircraft's nose should have been "slightly inclined" to enable the plane to regain lift after it had gone into an aerodynamic stall.

"This is part of the general pilot training for any aircraft," the official said. He was not authorized to speak on that subject and asked not to be identified by name.