Probe raises questions about doomed flight's U-turn

French investigators said today that an Air France jet flying to Paris from Rio may have made an U-turn for some unexplained reason before it crashed in the Atlantic nearly a year ago.

The BEA air accident investigation office said the plane may have suddenly changed flight path based on the location of an area where the black box recorders are located in the Atlantic.

"If we find the wreckage in that zone, that means that the plane must have at some point made a U-turn, but why? No one knows. It is premature to speculate on possible scenarios," said BEA director Jean-Paul Troadec.

Air France Flight 447 was en route to Paris from Rio de Janeiro when it went down on June 1 in stormy weather, killing all 228 people on board.

The crash was the worst in Air France's 75-year history.

French officials last week said the navy had closed in on the black boxes following recent analysis of submarine sonar data collected in June and July last year. At that time, the black boxes were still emitting a signal.

A research vessel was dispatched to the area to carry out new searches, investigators said.

The black boxes are key to understanding what caused the disaster, which remains largely unexplained.

Pilots' unions and some of the relatives of crash victims have accused Air France and the manufacturer Airbus of ignoring longstanding problems with air speed monitors on its jets in the run-up to the disaster.

The BEA has said in a preliminary report on the crash that the jet's speed probes gave false readings and were "one of the factors" in the disaster but "not the sole cause".