PARIS/RIO DE JANEIRO - An Air France flight with 228 people on board was lost over the Atlantic Monday morning and is presumed to have crashed into the sea.

The Airbus A330-200, flight number AF 447, left Rio de Janeiro for Paris Sunday at 2203 GMT, but the plane lost radio contact with Brazilian air control at about 0130 GMT, the Chief Executive of Air France, Pierre-Henri Gourgeon, told journalists in Paris.

At about 0200 GMT, the aircraft entered a zone of severe turbulence and storms, Gourgeon said. Some 15 minutes later, a number of automatic maintenance messages from the aircraft signalled the failure of several electrical systems, he added.

“The plane could have been hit by lightning,” a spokesman for Air France said, suggesting the plane might have lost its power supply during a storm. But experts say that this scenario is unlikely.

Whatever the cause, Gourgeon was pessimistic about the plane’s fate. “We are undoubtedly facing an aviation catastrophe,” he said.

Transport Minister Dominique Bussereau said: “we don’t really understand what happened… We must unfortunately prepare for the worst.”

French RTL broadcaster quoted Brazilian air traffic controllers as saying there had been no distress message from the plane. As a result, some experts have not ruled out a terrorist attack.

French i-tele television reported that the plane was about 565 km from the Brazilian coast when contact with it was lost. At the time, it was flying at a speed of 840 kph at an altitude of 35,000 feet.

French President Nicolas Sarkozy was “greatly concerned” about the situation, according to his office, and a special crisis team and facilities have been set up at Paris’ Charles de Gaulle airport, where the plane had been due to land at 0910 GMT.

Sarkozy was expected to travel to the airport to talk with the passengers’ family members, who gathered there during the day to await news.

The Brazilian air force scrambled a search-and-rescue mission to the area around the archipelago of Fernando de Noronha, around 500 km off the northeast coast of Brazil.

A French military reconnaissance aircraft has also taken off from Senegal, on the West African coast, to take part in the search mission.

However, it was impossible to determine precisely where the plane went down, which means that it could be days before it is found.

Air France said the plane was carrying 216 passengers, including seven children and a baby, as well as a crew of 12.

Most of the passengers were believed to be Brazilian. However, the online edition of the daily Le Figaro cited the French interior ministry as saying that there were about 60 French nationals aboard, while France Info radio reported that at least 20 Germans were on the plane.

British Prime Minister Gordon Brown said Monday he feared there could have been Britons among the passengers.

“I do fear there may be some British citizens on board. We are doing all the checking that is necessary. I have been in touch with the Foreign Office,” he said.

According to Air France, the pilot of the plane was very experienced, having logged 11,000 flight hours, including 1,700 hours with Airbus A330/A340 aircraft.

Airbus said the plane was delivered to Air France in 2005 and had accumulated about 18,800 flight hours in some 2,500 flights.