Pilots wrestled with the controls of an Air France (AIRF.PA) airliner for more than four minutes before it plunged into the Atlantic with its nose up, killing all 228 people on board

Pilots wrestled with the controls of an Air France (AIRF.PA) airliner for more than four minutes before it plunged into the Atlantic with its nose up, killing all 228 people on board, French investigators said on Friday.

Aviation industry sources told Reuters pilots appeared to have acted contrary to normal procedures in raising, rather than lowering, its nose in response to an alert that the plane was about to lose lift or, in technical parlance, 'stall'.

But they said information from black boxes hauled up from the Atlantic floor earlier this month was still incomplete.

The 2009 emergency began with a stall warning two and a half hours into the Rio-Paris flight and nine minutes after the captain had left the cockpit for a rest period.

Shortly before, a junior pilot had told flight attendants to prepare for a "little bit of turbulence"

The Airbus (EAD.PA) A330 jet climbed to 38,000 feet and then began a dramatic three and a half minute descent, rolling from left to right, with the youngest of three pilots handing control to the second most senior pilot one minute before the crash.

The timeline was described in a note by France's BEA crash investigation authority, which said it was too early to give the causes of the crash ahead of a fuller report in the summer.

"These are so far just observations, not an understanding of the events," BEA director Jean-Paul Troadec told reporters.

The captain returned after "several attempts" to call him back to the cockpit but was not at the controls in the final moments, according to information gleaned from black boxes.

By the time the 58-year-old returned, just over a minute into the emergency, the aircraft was plunging at 10,000 feet a minute with its nose pointing up 15 degrees and at too high an angle compared to the onrushing air to provide lift.

The BEA said the reading of the black boxes suggested the crew were not able to determine how fast the plane was flying.

That echoes earlier findings which suggest the pitot tubes or speed sensors on the plane may have become iced up.

The airline said in a statement that the crew had demonstrated a "totally professional attitude". France's pilots union declined to comment.

"It's very emotional to see the unrolling minute by minute or second by second at some points of what happened," said John Clemes, vice president of the families' support group.

"You automatically think of your family member and how they were living through this. It's the events that caused the deaths of 228 people so it's traumatic and moving.

France's BEA crash investigation agency said pilots pulled the nose up at crucial moments as the aircraft became unstable and the aircraft generated an audible stall warning.

"The inputs made by the pilot flying were mainly nose-up," the BEA said in a timeline based on initial examination of the cockpit voice and data recorders.

A top aircraft industry safety consultant said the standard guidance in the Airbus pilot manual called for the pilot to push the control stick forward to force the plane's nose down in the event of a stall, which can lead to a loss of control.

"The BEA is now going to have to analyse and get to bottom of how crew handled this event," said Paul Hayes, safety director at Ascend Aviation, a UK-based aviation consultancy.

"The big question in my mind is why did the pilot flying (the aircraft) appear to continue to pull the nose up," he said.

"I must stress we are commenting and speculating on preliminary factual information, which will need analysing."

ADVICE TO PILOTS

The BEA report was strictly factual and did not allocate any blame or cause of the crash on June 1, 2009.

"These are so far just observations, not an understanding of the events," BEA director Jean-Paul Troadec told reporters.

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