"Air France addresses its sincere condolences to the families and friends of the passengers and crew members who were on board flight number AF 447," the airline said in a statement on its website.
Nicolas Sarkozy, the French president, met the shocked relatives as it became increasingly likely that an accident had occurred.
"I told them the truth, which is that the prospects of finding any survivors are very slim," he said afterwards.
"It's a catastrophe the likes of which Air France has never seen".
Al Jazeera's Estelle Youssouffa, reporting from outside Charles de Gaulle, said that many of the relatives had spent long hours at the airport on Monday.
"Those people who were hoping to be reunited with their loves hours ago ... are being kept secluded from media attention, sheltered from the public prying into their privacy," she said.
In Brazil, about 50 people gathered at Galeao airport in an attempt to find out what had happened to their loved ones.
"I called Air France right away, and they told me they didn't have information. That's why I decided to come to the airport," Bernado, who declined to give his last name, told the AFP news agency.
He said that his brother and sister-in-law were two of the 216 passengers on the flight.
Jorge Asuncao, an Air France spokesman in Rio De Janeiro, said there were 80 Brazilian passengers, 73 French, 18 Germans, nine Italians, six Americans, five Chinese, four Hungarians, two Spanish, two British, two Moroccans and two Irish.
There were also nationals from Angola, Argentina, Belgium, Iceland, Norway, the Philippines, Poland, Romania, Russia, Slovakia, Sweden, Switzerland and Turkey, he said.
|Sarkozy, right, said he had told the relatives that the chances of survivors were 'slim' [AFP]
Air France said that doctors and psychologists would be on hand at the airport and at a hotel in a southern suburb of Rio. The French consulate was also planning to open facilities to support relatives.
A French couple at Rio's international airport said of their "miraculous" escape.
"We should have been on the plane," Claude Jaffiol, a medical professor, said.
Jaffiol explained he had been in Brasilia, the capital, for a seminar and had stayed for a few days of tourism, but decided to fly home earlier than planned.
Despite having "moved heaven and Earth" to try to get on the flight, they were turned away because it was full, he said.