The Airbus A320 jet operated by Germanwings, the budget airline owned by Lufthansa, was en route from Barcelona to Düsseldorf when it lost height rapidly, descending 30,000ft in eight minutes before crashing in the southern French Alps.
The French authorities launched a recovery operation, involving 600 gendarmes and 10 helicopters but were hampered by the inaccessible terrain.
The crash site, northeast of Dignes-les-Bains in Haute Provence, is 7km from the nearest road and at an altitude of 1,600 metres.
Bernard Cazeneuve, the French interior minister, said investigators would examine the black box recorder overnight to shed more light on the reasons for the crash. They will hold a press conference on Wednesday afternoon.
Speaking at the French National Assembly, Manuel Valls, the prime minister, said no hypothesis could be ruled out.
“It’s a tragedy,” President François Hollande said in a television address, adding that the circumstances of the crash led the government to believe there may not be any survivors.
The flight was carrying 144 passengers and six crew. Among them were 67 Germans and 45 Spaniards.
The passengers included 16 students and two teachers from a German school. The Spanish government has announced three days of national mourning.
Mr Hollande spoke to Angela Merkel, the German chancellor, to express his condolences. Ms Merkel and Mariano Rajoy, the Spanish prime minister, will join the French president at the crash scene on Wednesday, the Elysée Palace said.
Television footage of the crash site showed debris, mostly in small pieces, strewn widely over the mountainside above a steep ravine.
A helicopter was able to land at the scene and the crew concluded that there were no survivors, Mr Valls told parliament.
Airbus said it was “trying to assess the situation”. It added: “Our thoughts are with those affected by this tragic event.” added,
The Germanwings aeroplane did not transmit a Mayday. It was air traffic controllers who sounded the alert after noting the aircraft’s loss of altitude and radio contact. The aeroplane disappeared from their radar at 10.53am local time.
Harro Ranter, chief executive of the Aviation Safety Network, an independent body that has an exhaustive database of every global aviation accident over the past 70 years, said it was “highly unusual for a western European airline to suffer an accident like this and at this flight phase”. Close to 40 per cent of accidents occur at the approach or landing stage, according to international safety data.
Mr Ranter said the aircraft appeared to have maintained a steady descent without “the more erratic flight path that might be typical for a loss of control. It appears to be a very strange accident”, he said.
Germanwings is a budget airline wholly owned by Lufthansa that was launched in 2002. It operates short-haul flights across Europe from its base in Cologne.
The crash of Flight 4U 9525 is the deadliest aviation accident in France since 180 people were killed when an aircraft crashed into a mountain in Corsica in 1981. In 2000, 113 people were killed when a Concorde crashed shortly after take-off from Paris’s Charles de Gaulle airport.
The Germanwings jet was 24 years old and has been owned by Lufthansa since 1991, according to online database airfleets.net. The company said there were “several” A320 planes of that age in operation within the group, and Mr Winkelman said they would not be grounded as a precaution.
The A320 is the workhorse of the aviation industry, with more than 6,000 of the single aisle aircraft in operation. An A320 takes off or lands every 2.5 seconds.
It was the A320 family that pioneered the commercial use of the fly by wire system, which replaces manual flight controls with an electronic system.
Reporting by Anne-Sylvaine Chassany and Michael Stothard in Paris, Peggy Hollinger, Mark Odell and Claer Barrett in London and Chris Bryant in Frankfurt
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