An Air France jet going from Rio de Janeiro to Paris may have turned around before it crashed last year, killing all 228 people aboard, officials said Monday.
The head of the French accident investigation agency said the plane could be found by Wednesday.
Pinging signals from the plane's flight recorders detected in the Atlantic depths last year were analyzed last week with the aid of new technology that helped narrow down the search zone to what turned out to be an unexpected location.
Lead investigator Alain Bouillard said that if the plane is found in the zone where signals came from, then that would suggest that it turned around after reaching the position that it last reported to air traffic controllers.
"It's a probable hypothesis," he said. "The question is why?"
The head of the French accident investigation agency BEA, Jean-Paul Troadec, said that sonar specialists from French company Thales continued to study the data from the initial search efforts, when the black box recorders were still emitting pings.
Using the newly analyzed information, search efforts are concentrated on a zone 10 kilometers by 20 kilometers, two thirds of which has been explored.
Troadec said investigators will first try to find remains of the plane, and then look for the black boxes, without which the cause of the crash may never be known. Submarine drones are scouring the area, he said.
"It's a relief and gives us hope in the search for truth," said Robert Soulas, who lost his daughter and son-in-law on Flight 447 and is part of an association that represents victims' family members.
But both Troadec and Soulas said they were being "prudent" and not jumping to any conclusions.