'Considering all the work that has been done and all we have at our disposal, I think we may be getting a bit closer to our goal,' said Paul-Louis Arslanian, director of the Investigation and Analysis Bureau (BEA) in charge of the technical inquiry into the disaster.

'The goal is to understand what happened,' Mr Arslanian told reporters at the Paris Air Show, in a briefing on the progress of the inquiry.

Air France flight AF 447 plunged into the ocean on June 1 as it was flying from Rio de Janeiro to Paris with 228 people on board. The cause of the disaster is unknown.

'We are doing all we can to recover the flight recorders and bodies, and we cannot say today what we will succeed in doing,' Mr Arslanian said, adding: 'It is virtually certain that we will not recover the entire aircraft.'

'We are doing all we can, and it is very difficult,' he stressed, warning it was impossible to accurately predict the investigation's chances of success.

Searchers off Brazil on Tuesday found another body from the Airbus A330 jet, bringing the total recovered by the Brazilian and French navies to 50.

An international search team is scouring an area of 19,000 square kilometres, with the focus now on locating the 'black box' recorders that could hold the key to its plunge into the Atlantic.

A French nuclear submarine, 'Emeraude', has been patrolling the area where the plane went down in the hopes that its ultrasensitive sonars will pick up signals emitted by the flight recorders.

Two other ships brought in by France are supposed to work with two 'pinger locators', sonars installed on a kilometers-long cable supplied by the US military, while the French underwater exploration vessel 'Pourquoi pas' is also in the area with a submarine and a robot.

From Wednesday, authorities are to evaluate every two days whether to continue the operation. -- AFP

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Search for Flight 447 continues