Officials said the Airbus A330-200 sent automated messages of electrical failure and pressure loss as it hit turbulence, vanishing from the radar early in its flight from Rio de Janeiro to Charles de Gaulle airport in Paris.
Brazil and France have scrambled search and rescue aircraft on both sides of the Atlantic, but with a vast area to scour, there were dwindling hopes of finding survivors.
The loss of a relatively new model of one of the aviation sector's most reliable and state-of-the-art aircraft has stunned analysts who say it would take extremely violent weather to bring down such a large jet.
Former Airbus pilot John Wiley told CNN that speculation lightning had brought down the plane was likely to prove unfounded since most modern passenger aircraft were capable of withstanding direct strikes.
Jun 1, 2009
Air France jet vanishes over Atlantic Ocean
An Air France plane is feared to have crashed in the Atlantic with 228 people aboard reported electrical problems in stormy weather before it lost contact.