The nuclear submarine has less than three weeks to find the black boxes
A French nuclear submarine has arrived at the scene of the Air France crash in the ocean off Brazil to start searching for the flight's data recorders.
The "black boxes", which emit a locator signal for about 30 days, could be up to 6,100m (20,000ft) deep, on the bed of the Atlantic.
They could provide vital clues as to why the Airbus A330 crashed on 1 June.
Brazilian air and sea searches have now recovered 41 bodies from the plane, which had 228 people on board.
The submarine, and Brazilian naval and air forces, have a large and remote area of ocean to search.
Debris from the plane, which was flying from Rio de Janeiro to Paris, has been found some 1,000km (600 miles) north-east of the Fernando de Noronha islands. The islands are about 320km off the north-eastern coast of Brazil.
French military spokesman Captain Christophe Prazuck said the submarine - the Emeraude - should be able to cover an area of 26 sq km each day. It has advanced sonar equipment on board.
"There are big uncertainties about the accident site, the ocean floor is rugged... so it's going to be very difficult," he told French radio.
"It's going to be very complicated and we're going to need a lot of luck" to find the plane's data recorders.
The US is also joining the search, sending two sophisticated listening devices, which will be deployed on two large vessels hired by France. They will be towed in a grid pattern across the search area.
If the aircraft's two black boxes are located, a mini-submarine called the Nautile will be sent down to retrieve them. The vessel, which has a crew of three and is about 8m long, is the same one which explored the wreck of the Titanic.
On Monday, a search team recovered a large tail section. The Brazilian military released photographs of divers securing the tail fin, which was painted in Air France colours.
Officials said the first bodies had been taken by helicopter to the Fernando de Noronha islands.
SEARCH FOR FLIGHT AF 447
1 June: Contact lost with plane over mid-Atlantic
2 June: First debris spotted from the air includes an airline seat. Brazilian defence minister says debris is from missing plane
3 June: More debris spotted, including a 7m-wide chunk of metal. Fuel slick seen on surface
4 June: Recovered buoys and pallet said to be from plane. Officials later retract statement
6 June: First two bodies, plus suitcase and backpack found, along with seat from the plane
7 June: Fourteen additional bodies recovered, taking total to 16
8 June: Large tail fin section found
They were due to be moved to the Brazilian city of Recife on Wednesday, where a temporary mortuary has been established.
Investigators hope they can use dental records and DNA tests to confirm identities. DNA samples have been taken from relatives of the plane's passengers to help with the process.
Investigators have so far focused on whether the plane's speed sensors stopped working properly just before it crashed in turbulent weather.
French officials have said the sensors could have iced over, meaning pilots may have flown into a storm without knowing their speed.
Air France has said it is stepping up the process of replacing speed monitors on board its Airbus planes.
The company said it first noticed problems with speed monitors a year ago and began replacing them a few weeks before the accident.
But investigators have yet to confirm what role faulty sensors might have played in the crash.