A plane operated by the budget carrier subsidiary of Germany's Lufthansa crashed in a remote part of the French Alps yesterday, killing all 150 on board.
It was the worst plane disaster in mainland France for four decades.
Germanwings said the Airbus A320 dived for eight minutes before slamming into a snowbound inaccessible mountainous area in southeastern France.
French officials said no distress signal had been sent out.
The plane, carrying 144 mainly Spanish and German passengers and six crew, was travelling from Barcelona to Dusseldorf, Germany, when it came down near the ski resort of Barcelonnette.
French Prime Minister Manuel Valls said there were no survivors, adding that the authorities "can't rule out any theory" about the cause of the disaster.
Spanish authorities said 16 German teenagers on a school trip were believed to be on board the doomed plane.
It was the first fatal accident in the history of Germanwings, and the deadliest on the French mainland since 1974, when a Turkish Airlines aircraft crashed, killing 346.
French President Francois Hollande said: "We will determine what caused the crash."
He said the dead included Germans, Spaniards and "probably" Turks. Belgium said at least one of its nationals was on board.
A crisis room has been set up in the area between Barcelonette and Digne-les-Bains, along with an emergency flight control centre to co-ordinate operation at the crash site.
Local resident Francoise Pie said: "Ground access is horrible. I know the Estrop massif; it's a very high, mountainous area, very steep, and it's terrible to get there except by air, during winter."
A French police helicopter dispatched to the crash site reported spotting debris in a mountain range known as Les Trois Eveches at an altitude of 1400m.
German Chancellor Angela Merkel said she was "shocked" by news of the accident and would immediately travel to the crash site. Spanish King Felipe VI cut short his state visit to France on hearing of the tragedy.
French civil aviation authorities said they lost contact with the plane and declared that it was in distress at 10.30am (11.30am, SA time).
But the aircraft's crew did not send a distress signal, the civil aviation authorities said .
"The crew did not send a Mayday. It was air traffic control that decided to declare that the plane was in distress because there was no contact with the crew."
Shares in Airbus and Lufthansa were both down after news of the crash broke.
