A 30 minute recording obtained from the cockpit voice recorder of flight 4U 9525 provides the clearest indication yet as to what happened on board.
Investigators have listened closely to the audio and say the co-pilot, 28-year-old Andreas Lubitz, appears to have deliberately brought the plane down.
So how did this final half hour unfold?
Germanwings flight 4U 9525 took off from Barcelona Airport heading for Duesseldorf, with 150 people on board, at 09:01 GMT on 24 March.
The Airbus 320 began travelling over the sea towards France, taking about half an hour to climb to 38,000ft (11,600m).
It should have been a two-hour flight.
At 09:30 GMT the plane made its final contact with air traffic control - a routine message about permission to continue on its route. Everything seemed to be going as planned.
A minute later at 09:31 GMT, the plane began its descent.