Germanwings, a budget airline, crashed in southern France as it traveled from Barcelona to Dusseldorf, according to aviation officials.
French Prime Minister Manuel Valls believed around 150 people were on board and are feared dead.
“The cause is at present unknown,” he told reporters.
A spokesman for the DGAC aviation authority said the airplane crashed near the town of Barcelonnette about 100 km (65 miles) north of the French Riviera city of Nice.
Lufthansa’s Germanwings unit said it was as yet unable to verify reports of the crash.