Ocean currents have pushed the remnants far and wide since the jet went down May 31 with 228 people on board.
The black boxes provide the best hope of unraveling why the Airbus A330-200 aircraft apparently broke up in midair and plunged into sea.
With more punishing ocean storms hitting the area as early as Thursday and the possibility that the boxes could have come to rest amid jagged underwater mountains, finding them is a formidable task.
"There are big uncertainties about the accident site, the ocean floor is rugged ... so it's going to be very difficult," French armed forces spokesman Christophe Prazuck told France-Info radio.
"It's going to be very complicated and we're going to need a lot of luck."
The nuclear sub Emeraude plans to trawl 13 square miles (35 square kilometers) a day, using sonar to try to pick up the boxes' acoustic beacons before they start to fade in three more weeks. The submarine will be reinforced by two U.S. underwater audio devices capable of picking up signals even at a depth of 20,000 feet (6,100 meters).
If the boxes are located, the Emeraude will launch the unmanned mini-sub Nautile, which had a key role in the search for the wreckage of the Titanic, to recover them.
The first of the two U.S. pinger locators was loaded Wednesday onto a Dutch search contracted by French investigators in the northern city of Natal, and should reach the search area by Sunday.
A second Dutch ship is expected to pick up the other device this weekend. Each one will be slowly towed in a grid pattern while 10-person teams watch for signals. U.S. Air Force Col. Willie Berges said.
The French magazine L'Express reported that French intelligence services had matched the names of two passengers on board Flight 447 with those of suspects linked to Islamic terrorism. But it noted the passengers' birth dates were not available, and that it might only be a case of people with similar names. The names themselves were not reported.
But a senior French internal security official, speaking on condition of anonymity because of the nature of her job, said French security "didn't find any suspicious names" on the passenger list. "That doesn't mean there aren't on a suspect list, but it's not ours," she told The Associated Press.
Other police and intelligence agencies involved said they also had no information about terrorist connections to Flight 447.
Brazil's federal police have examined airport video footage of passengers to help identify the bodies, not to pursue any suspicions of terrorism, according to an agency spokeswoman who insisted on anonymity because she was not authorized to discuss the matter.
A total of 41 bodies have been recovered so far, and are being flown daily to Recife, where investigators hope to identify them and uncover clues based on their injuries.
Prazuck told Associated Press Television News that a French frigate, the Ventose, had already gathered 130 pieces of debris, big and small. The debris was being cleaned of salt and was to be taken to an undisclosed location for further analysis, he said.
Without key information from the Airbus A330's missing data recorders, investigators have focused on the possibility that external speed monitors - Pitot tubes - iced over and gave false readings to the plane's computers as it flew into thunderstorms.
Airlines around the world have begun replacing Pitot tubes on their aircraft. And the European Aviation Safety Agency, responsible for the certification of Airbus planes, said it was "analyzing data with a view to issuing mandatory corrective action" following reports about the possible malfunctioning of the Pitot tubes. But it also said the A330 and other Airbus aircraft are safe to operate.
An important part of the investigation relies on a burst of 24 automatic messages the plane sent during its final minutes of flight. They show that the autopilot was not on, but it was not clear if it had been switched off by the pilots or stopped working due to conflicting airspeed readings.
About 70 airlines operate some 600 A330 planes similar to the doomed Air France jet, and the Pitots being replaced are made by France's Thales Group.
NEW YORK AND TRI-STATE AREA NEWS
USEFUL LINKS:
REPORT A TYPO || GET WIDGET || VIDEO: Eyewitness News
VIDEO: ABC News || VIEWER PHOTOS & VIDEOS || VIDEO: Latest news from AP
