The co-pilot of the Airbus A320 which crashed in the French Alps appeared to want to ‘destroy the plane’, according to French prosecutors.

Andreas Lubitz put the plane into a descent after the captain had left the cockpit, Marseille prosecutor Brice Robin told reporters.

Evidence from the black box flight recorder suggests he then refused to open the cockpit door to the captain.

The captain knocked on the door and asked to be let in and there was no answer from the co-pilot. Later there are the sounds of attempts to break down the door, the prosecutor said.

Mr Robin said the co-pilot was alone at the controls and “intentionally” sent the plane into the doomed descent.

He said pounding could be heard on the door during the final minutes before the crash as alarms sounded.

The co-pilot “voluntarily” refused to open the door and his breathing was normal throughout the final minutes of the flight.

Mr Robin identified the pilot as a German national and who had never been flagged as a terrorist.

For the first 20 minutes the two pilots talked in a normal fashion and were as courteous as two normal pilots would be.

The information has been pulled from the black box cockpit voice recorder.