The Airbus A320 - flight 4U 9525 - went down between Digne and Barcelonnette. None of the 144 passengers or six crew is expected to have survived.
The plane crashed after an eight-minute descent, an official said. It is not clear if it sent a distress signal.
The dead are believed to include 16 German schoolchildren. French and German leaders have expressed shock.
"This is the hour in which we all feel deep sorrow," German Chancellor Angela Merkel told reporters, adding that she was planning to travel to the crash site. (+ BBC videos) » | Tuesday, March 24, 2015