The Germanwings flight from Barcelona to Düsseldorf rapidly descended for eight minutes before crashing without sending any distress calls.
It is believed to be the biggest single loss of life suffered by the 60-year-old Lufthansa Group, which owns the budget airline.
Foreign Secretary Philip Hammond said it was “sadly likely” there were some British nationals on board.
One of the Airbus A320’s “black boxes” has been recovered from the Meolans-Revels crash site near the Pra Loup ski resort, which could give some of the first clues about what happened to flight 4U 9525. Several larger pieces appeared to be part of the fuselage of the plane, including six windows.
Gilbert Sauvan, president of the general council of the Alpes-de-Haute-Provence, said: “Everything is pulverised.” He said the largest pieces of debris were the size of a small car.
There were 144 passengers on board, including two babies, with four cabin crew and two pilots. It is believed they included 67 Germans and 45 Spaniards.
Ten helicopters and a military plane have been sent to the crash site, which is only accessible by air.
The Airbus A320 involved is one of the workhorses of European aviation, including a significant part of the easyJet and British Airways fleets which serve Scotland.
The 24-year-old aircraft – which was used to connect Edinburgh with Cologne in Germany – had a normal service check in Düsseldorf on Monday and its last major check-up was in the summer of 2013.
Its captain had more than ten years’ experience with Germanwings and Lufthansa.
A school in Germany was “assuming the worst” after it confirmed 16 of its students, aged 15-16, and two teachers, had boarded the flight.
German chancellor Angela Merkel, who is due to visit the crash site today, said: “We still don’t know much beyond the bare information on the flight, and there should be no speculation on the cause of the crash. The crash . . . is a shock that plunges us in Germany, the French and the Spanish into deep sorrow.”
She said her thoughts were “with those people who so suddenly lost their lives, among them many compatriots”.
French president François Hollande called the crash “a tragedy on our soil”.
Airline chief executive Carsten Spohr said: “This is a dark day for Lufthansa.”
The last time a passenger jet crashed in France was the Concorde disaster in 2000, which left 113 dead – 109 in the plane and four on the ground.
EasyJet and British Airways said they were awaiting any instructions from aviation safety authorities. Many of BA’s 61 A320s are maintained at its engineering base at Glasgow Airport. A spokeswoman for easyJet said: “Safety is our highest priority.”