Alps crash horror: The crucial eight minutes are key to discovering cause
Flight 4U9525 from Barcelona to Düsseldorf had reached a cruising altitude of 38,000ft at 10.45am with 150 passengers and crew on board.
The Airbus A320 began an unexplained descent before dropping off radar screens at 10.53am. Last night, former air accident investigators were quick to focus on that time window, with the aircraft's angle of attack sensors among the main areas of attention.
Nothing will be certain until the black box recorders are analysed, but these sensors will be vital in the investigation as they assist the crew in determining an aircraft's speed. Crucially, in the event of a stall they can automatically pitch an aircraft's nose downwards, unless the crew overrides them.
Much has already been made of the fact that the sensors fitted to this type of Airbus were covered by a wider Emergency Airworthiness Directive issued in December by the European Aviation Safety Agency (EASA). This came after they were thought to have contributed to a Lufthansa aircraft briefly falling into an uncontrollable dive over Spain. In that case pilots managed to regain control.
A spokesperson for Airbus said last night that there was "nothing at all to indicate" the fault raised by the EASA directive and the Germanwings accident were "linked".
But James Healy-Pratt, a specialist aviation lawyer for Stewarts Law, said the sensors would "almost certainly" be part of the investigation. He said: "It is far too early to speculate, but French investigators will almost certainly be looking at the Lufthansa incident and the EASA directive will be looked at very closely."
The Airbus A320 is a generally safe aircraft type and a bird strike or simultaneous engine failure is thought to be very unlikely, according to Phil Giles, formerly with the UK's Air Accidents Investigation Branch.
He said: "What's remarkable about this incident is the measure of control it appears there was as the plane descended from its cruising altitude to impact."