The Air France plane that crashed into the Atlantic last month with 228 people on board was not destroyed in mid-air but hit the water intact and at high speed, French investigators said on Thursday.
Flight AF 447 went missing during a flight from Rio de Janeiro to Paris on June 1. The exact cause of the disaster is not yet known.
"The plane was not destroyed while it was in flight. It seems to have hit the surface of the water in the direction of flight and with a strong vertical acceleration," said Alain Bouillard, who is leading the investigation on behalf of France's BEA air accident board.
Bouillard said control of the flight was supposed to have passed from air traffic controllers in Brazil to their counterparts in Senegal, but that never happened.
He said the pilots of flight AF 447 had tried three times to connect to a data system in the Senegalese capital Dakar, but had failed, apparently because Dakar had never received the flight plan.
"This is not normal," he said, adding that investigators were also trying to find out why it took six hours after the plane disappeared before an emergency was declared.
He said the search for the flight recorders, or black boxes, from the Airbus A330 aircraft would continue until July 10. The recorders emit a signal for a limited time.
He also reiterated that France had not yet been granted access to autopsy reports on bodies taken to Brazil.
Despite the June 1 disaster, investigators see no wider concerns that would indicate the need to ground Airbus A330 aircraft.
"The information available today does not indicate any such need," Philip Swan, an adviser to France's BEA air accident board, told a news conference.
"They have flown tens of million of hours and there are 660 of them flying," he said.
"For me there is no problem," added Bouillard.