Passenger airliner Airbus A320 sent a 'distress signal' before plunging into the French Alps, according to reports.
French President Francois Hollande has confirmed no survivors are expected after the aeroplane with 150 people on board crashed.
According to Flightradar24, which keeps track of aircraft across the world, the Airbus was descending with a rate of about 3,000-4,000ft per minute.
The tracking agency also added the flight climbed to 38,000ft before it started to descend and lose signal at about 6,800ft.
French aviation authorities confirmed they detecting a emergency signal from the plane 46 minutes after its take-off from Barcelona. The wreckage of the flight has already been spotted.
According to the French Civil Aviation Authority (DGAE) there had been what is known as a distress FA, which happens when a plane disappears from radars, or blacks out and all communications are cut with the cockpit.
It disappeared from both radars and audio waves with control towers, the French civil aviation authority said.
No climatic event could explain this crash, the DGAE said.
An investigation has been opened by the French Ministry of Interior.
Hollande also added the crash site was "a difficult area to access" as emergency measures had already been scrambled.
The passenger airliner, operated by low-cost airlines Germanwings, was travelling from Barcelona, Spain, en route to Dusseldorf when it went down.