It was to be followed by two other French planes based in Dakar, and a naval vessel currently cruising in the Gulf of Guinea, several days' sailing away.
Spain and Senegal have also sent planes to help in the search.
Brazil has sent out seven air force planes and three naval ships to help in the search, far off the north-eastern Brazilian coast. Some aircraft were not expected until Wednesday morning.
Air force spokesman Col Jorge Amaral said earlier they were trying to reach the point from where the aircraft had last made contact, about 1,200km (745 miles) north-east of Natal.
But Maria Celina Rodrigues, the Brazilian consul in Paris, said the depth of the ocean would make it difficult for searchers.
"They are hoping they can find debris, pieces, lifejackets that eventually float, but that takes some time," she told the Associated Press.
The Brazilian authorities have also said they are investigating a possible sighting of wreckage in the area, reported Reuters news agency.
The crew of a TAM Linhas Aereas flight travelling over the area in the other direction shortly after the Airbus' last signal had reported seeing "bright spots" in the ocean about 1,300 km (800 miles) from the Fernando de Noronha archipelago off Brazil's north-eastern coast.
The plane's automatic reports were generated at around 0200 GMT on Monday, about four hours after Flight AF 447 left Rio de Janeiro, and as it was heading through turbulence towards the west African coast.
Missing man Arthur Coakley’s wife, Patricia, and his business partner Ken Pearce
"A succession of a dozen technical messages" showed that "several electrical systems had broken down" which caused a "totally unprecedented situation in the plane", said Mr Gourgeon.
"It is probable that it was shortly after these messages that the impact in the Atlantic came," he told reporters at Charles de Gaulle airport, where the airliner had been due to land.
Flight AF 447 was flying at an altitude of 10,670m (35,000ft) shortly before it went missing.
A meteorologist who spoke to the Associated Press said tropical thunderstorms in the Atlantic could tower up to 15,240m (50,000ft).
"At the altitude it was flying, it's possible that the Air France plane flew directly into the most charged part of the storm - the top," said Henry Margusity, senior meteorologist for AccuWeather.com.
French officials have stressed that the plane's captain was very experienced, clocking up more than 11,000 hours of flight.
Crisis centres have been set up at Charles de Gaulle airport in Paris and Rio's Tom Jobim international airport.
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