Search crews have now recovered 41 bodies from an area in the Atlantic where an Air France passenger plane went down over a week ago.

Three young Irish doctors were among the 228 people on board the aircraft when it plunged into the sea in unexplained circumstances, four hours into a flight from Rio de Janeiro to Paris.

A French military submarine is due in the crash zone, around 1,100km off Brazil's northeast coast, to search for the plane's flight data recorder, which may contain vital clues.

Two French tugboats are also to be equipped with hi-tech underwater locators that could pick up signals from the black box, believed to lie on the seabed up to 6,000m below.

A French research vessel is also expected to arrive in the area tomorrow, carrying deep-sea mini-subs that could be used to recover the black boxes.

No distress call was received from the pilots of the doomed plane, but there was a series of 24 data alerts sent by the plane in its final minutes.

Those showed the cockpit was getting faulty airspeed readings and autopilot was suddenly disengaged.

Navigation and power systems also failed.

Those have focused suspicions on the plane's exterior airspeed sensors, which some suspect may have iced over at high altitude, leaving pilots unable to know how fast they were going.

Plane-maker Airbus and Air France say older probes have been problematic on other Airbus A330s and A340s.