France's Charles de Gaulle airport has set up a crisis centre to help relatives of passengers of an Airbus 330-200 flight that has gone missing over the Atlantic after a possible lightning strike.
The plane sent out a message four hours after leaving Rio de Janeiro with 216 passengers and 12 crew on board, reporting a short circuit.
Flight AF447 left Rio at 19.00 local time and is thought to have disappeared 300km north-east of the Brazilan city of Natal.
Air France head of communications Francois Brousse said that the plane might have been struck by lightning and that there had been no communications with it for some time.
"Nothing on Spanish radar, nothing on Moroccan radar, nothing on French radar - we seriously have to fear the worst," he added.
The Paris airport has set up a special area in its second terminal to receive people awaiting the flight.
Relatives are being kept away from journalists and counseled by airport staff.
Air France has opened a telephone hotline for friends and relatives.