The French nuclear submarine arrived off the coast of Brazil this morning to search for Air France flight 447's flight recorders.
The sub, the Emeraude, which is equipped with high-tech sonar equipment, joins search teams from several countries in the race against time to find these flight recorders.
"Its mission is to detect the acoustic signals sent by the black boxes," French military spokesman Christophe Prazuck told ABC News. "It is capable on a daily basis of patrolling in a zone of 20 nautical by 20 nautical miles, 36 kilometers by 36 kilometers (22 miles by 22 miles), to detect acoustic signals sent by the black boxes."
"It will change zones every day," he said.
The Emeraude will work in conjunction with a research vessel from the French Research Institute for Exploitation of the Sea, the Pourquoi Pas, that carries underwater robots and is due to arrive in the region Friday.
The Pourquoi Pas is the only vessel in the French arsenal that carries suitable devices to retrieve and locate the black boxes, if their signals are ever detected.
"This special submarine is on board the Ifremer's sea research vessel Pourquoi Pas and is expected in the area Friday," Prazuck told ABC News.
In all, there are 400 French military personnel in the area.
A total of 41 bodies have now been found in the Atlantic Ocean from Air France flight 447, the airline announced Tuesday evening.
And as divers continue to recover remains and wreckage from the crash site, airlines worldwide scramble to replace plane speed sensors on a number of Airbus jets.
Investigators looking into the accident believe speed sensors malfunctioned on the flight, and the problem could have caused the plane to fly at an unsafe speed.
Now Delta, US Airways and United, which flies a different model of Airbus, are rushing to finish replacing their sensors. Faulty speed readings can cause the jet to fly dangerously slow or fast.
It's not known for sure whether the sensors contributed to the crash 10 days ago, but pilots at Air France aren't taking chances. They've pressured the airline to quickly upgrade the speed sensors, called pitot tubes.
"We are really concerned," said Louis Jobard of Air France's pilots' union. "We have had some incidents, you know, before, reported on the Airbus 330 and Airbus 340 with the old type of pitot sensor."
The speed sensor changeover was recommended by Airbus 17 months ago, but it's common for airlines to take their time on work that is considered noncritical. Airbus had recommended changing the sensors because of reliability issues, and Air France had noticed sensors icing up on some flights.
The sensors had not yet been changed on flight 447, which former National Transportation Safety Board managing director Peter Goelz said was "not unusual."
"The recommendation that was made to Air France was not an emergency recommendation," Goelz said. "It was a recommendation that could be completed over time. And given the economics of the airline industry now, no air carrier wants to take their plane out of service unnecessarily."
In the Air France crash, pilots weren't just struggling with equipment problems: It was likely a series of failures and mishaps that led to the tragedy.