Air France 447 - Plane's recorders may never be found, searchers say
PARIS, France (CNN) -- French officials -- who said there is now no hope that anyone survived the crash of an Air France jet that plunged into the Atlantic -- said Wednesday they may never find the doomed jets flight data recorders.
A French AWACS reconnaissance aircraft prepares to leave its Dakar, Senegal base to search the crash zone.
A memorial for the victims of Flight AF 447, which included 61 people from France, 58 Brazilians, 26 Germans and people from 29 other countries, will take place at the Notre Dame Cathedral in Paris at 10 a.m. ET (4 p.m. GMT). Brazil has declared three days of mourning.
Air France CEO Pierre-Henri Gourgeon said aircraft encountered heavy turbulence about 02:15 a.m. local time Monday (10:15 p.m. ET Sunday). At that point, the plane's automatic system initiated a four-minute exchange of messages to the company's maintenance computers, indicating "several pieces of aircraft equipment were at fault or had broken down."
The jet, which was flying at 35,000 feet and at 521 mph, also sent a warning that it had lost pressure, the Brazilian air force said. Its last known contact occurred at 02:33 a.m., the Brazilian air force spokesman added. 
Map of Flight AF 447's flightpath »
"We need time to reach the recorders," said Paul-Louis Arslanian, head of France's Accident Investigation Bureau.
The recorders give off a locator signal that lasts for up to 30 days, and the French government has sent a research vessel with a deep-diving submersible on board to the area where the plane's debris was found.
French officials said weather conditions at the site -- believed to be a major factor in the crash -- remain "extremely difficult" and the depth of the Atlantic near the sites where wreckage was found is around 7,000 meters (21,000 feet).
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"Even in history ... recorders from time to time were found after the 30 days. But I'm not so optimistic," said Arslanian at a press conference Wednesday. "It's not only deep it's also very mountainous at that place of the ocean."
Arslanian said answers on what caused the crash could take a long time.
"It could be long, we can not do with 80 percent understanding," said Arslanian. "This catastrophe is the worst that our country has known in our country's air history."
He said there appeared to be no problems with Flight AF 447 before take-off, but that everything had to be "checked and verified."
On Tuesday authorities found debris from the jet in two separate debris fields 60 km apart located about 650 km (400 miles) northeast of the Fernando de Noronha Islands, an archipelago 355 kilometers (220 miles) off the northeast coast of Brazil.
Among the wreckage was an airplane seat, metal debris, an orange float, a drum and an oil spill, French officials said.
French investigators were first mobilized on Monday, with four teams set up to conduct the probe. One has been tasked with recovering the wreck and flight recorders, the second group are looking at the aircraft's maintenance history, the third checking the operations of the plane, and the last group studying the plane's systems and equipment.
The investigation's team leader, Alain Bouillard, said their first preliminary report would be submitted by the end of June.
