One of the two pilots flying the doomed Germanwings flight was locked out of the cockpit before the aircraft crashed into a remote region of the French Alps.
Audio taken from the black box voice recorder that was salvaged from the obliterated wreckage of the Airbus A320 indicates the pilot left the cockpit and could not re-enter, an official told the New York Times.
A senior military official involved in the investigation said the pilot is heard knocking lightly on the door of the cockpit before hitting the door harder when he gets no answer.
It indicates that just one of the two pilots on board was flying the plane – and that the second became panicked after he was unable to get back into the cockpit.
The revelation is the first insight into what took place on the aircraft in the moments before the plane (inset) plummeted into the mountainside, killing all 150 people on board.