Lubitz tested altitude settings - report

Andreas Lubitz competes at the Airportrun in Hamburg, northern Germany. Photo / Michael Mueller

Andreas Lubitz, the pilot who is believed to have deliberately crashed his Germanwings plane into a mountain, may have rehearsed the descent on an earlier flight, says a preliminary French air accident report.

The co-pilot put the Airbus 320 into a descent on an earlier flight from Dusseldorf to Barcelona on March 24, the report found. It is not clear whether it was a practice run or an aborted attempt to crash the aircraft.

Hours later, on the return leg to Dusseldorf, Germanwings Flight 4U9525 crashed into the French Alps, killing 150.

Lubitz "intentionally" altered the autopilot settings "to order the aeroplane to descend until it collided with the terrain".

The report by France's air accident bureau, BEA, disclosed that Lubitz had made similar changes to the autopilot during the previous flight.

None of the changes then had a noticeable effect on the aircraft's trajectory, Remi Jouty, the BEA director, said. "The plane had already commenced its descent."

On both occasions, Lubitz waited until the captain had left the cockpit to relieve himself.