Jean-Louis Borloo, the French minister in charge of transport, said hijacking had been ruled out.
|The plane lost radio contact over the Atlantic while flying from Rio de Janeiro to Paris|
"It is the kind of jet made to handle this kind of circumstance but there must have been a build-up of circumstances," he said.
Barry Gromett, a meteorologist at the London Weather Centre, said that the aircraft was passing through an area known as the Intertropical Convergence Zone.
"It is a zone in the tropics where you can have particularly deep thunder clouds," he said.