Pilot locked out of cockpit before crash

One of the two pilots on the doomed Germanwings flight was apparently locked out of the cockpit before the plane crashed in the French Alps.

Cockpit recordings recovered from the crash site indicated one of the seats was pushed back and the door opened and closed, followed by the sound of knocking, said a source close to the investigation.

The source said "there was no more conversation from that point until the crash".

An alarm indicating the proximity of the ground could be heard before the impact, which killed all 150 people on board.

The pilots had been speaking normally and in German at the start of Flight 4U9525. The source could not say if it was the captain or the first officer who had left the cockpit.

The cockpit voice recorder was found late on Tuesday, several hours after the crash of the budget flight from Barcelona to Duesseldorf, and the data analysed on Wednesday afternoon.

The Airbus A320 suddenly began a fatal eight-minute descent shortly after reaching cruising altitude.

No distress signal was sent and the crew failed to respond to desperate attempts at contact from ground control.