The doomed Air France airliner that crashed into the sea killing all 228 on board may have been trying to return for an emergency landing at the time, aviation experts said today.
Searchers found a plane seat, a life jacket, metallic debris and signs of fuel were in the middle of the Atlantic.
The debris was spotted from the air about 410 miles north of the Brazilian island of Fernando de Noronha, roughly along the path that the jet was taking before it disappeared, said a Brazilian Air Force spokesman.
There were no signs of life in two sightings of separate debris areas about 35 miles apart.
"The locations where the objects were found are towards the right of the point where the last signal of the plane was emitted," said the spokesman. "That suggests that it might have tried to make a turn, maybe to return to Fernando de Noronha, but that is just a hypothesis."
He said authorities would not be able to confirm that the debris is from the plane until ships arrive in the area tomorrow.
The discovery came more than 24 hours after the jet bound from Rio de Janeiro to Paris went down in an area of massive thunderstorms. Investigators have still no idea why it crashed.
Rescuers were continuing to scan a vast sweep of ocean extending from far off north-east Brazil to waters off West Africa.
The four-year-old Airbus A330 was last heard from at 3.14am Irish time yesterday.
Investigators on both sides of the ocean were trying to determine what brought it down. Potential causes included shifting winds and hail from towering thunderheads, lightning or a combination of other factors.
The crew gave no verbal messages of distress before the crash, but the plane's system sent an automatic message just before it disappeared, reporting lost pressure and electrical failure.
The plane's cockpit and "black box" recorders could be thousands of feet below the surface but will emit radio tracing signals for 30 days.
French transport minister Jean-Louis Borloo said: "The race against the clock has begun".
He added lightning alone, even from a fierce tropical storm, probably couldn't have brought down the plane. "There really had to be a succession of extraordinary events to be able to explain this situation," he said.
France's defence minister Herve Morin said "we have no signs so far" of terrorism, but all theories must be studied.
The Airbus A330-200 was cruising normally at 35,000 feet and 522 mph just before it disappeared nearly four hours into the flight. No trouble was reported as the plane left radar contact, beyond Fernando de Noronha.
However, a line of towering thunderstorms were strung out just north of the equator and bands of extremely turbulent weather stretched across the Atlantic toward Africa.
France's junior minister for transport, Dominique Bussereau, said the plane sent "a kind of outburst" of automated messages just before it disappeared, "which means something serious happened, as eventually the circuits switched off".
The pilot had 11,000 hours of flying experience, including 1,700 hours flying this aircraft.