The Germanwings co-pilot suspected of deliberately crashing a plane into the French Alps practiced a descent on a previous flight on the same day, investigators say.
A preliminary report on the crash showed that Andreas Lubitz practiced entering the fatal descent settings on the outbound flight and ignored repeated attempts to contact him from both ground and air.
The changes in autopilot settings, mimicking those which crashed Germanwings flight 4U 9525 some two hours later, would barely have been noticeable because the jet was already descending, investigators said.
“I can’t speculate on what was happening inside his head; all I can say is that he changed this button to the minimum setting of 100 feet and he did it several times,” said Remi Jouty, director of the French BEA accident investigation agency.
Shortly after the aircraft had reached cruise height on the return flight from Barcelona to Dusselfdorf, on which all 150 aboard died, the captain told Lubitz he was leaving the cockpit and asked him to take over the radio.
Just over 30 seconds after the door closed, the 27-year-old entered the instruction he had previously rehearsed, ordering the plane to descend to 100 feet on autopilot — easily low enough to crash into the mountains ahead. He then altered another dial to speed the jet up.
The findings come from examination of cockpit voice recordings and flight data taken from the aircraft’s two black boxes.
Lubitz, 27, had suffered from severe depression in the past and a computer found in his home showed he had used the internet to research ways of committing suicide in the days leading up to the crash.
Prosecutors also found torn-up sick notes at his home showing he should not have flown on the day of the flight.
Cockpit audio recordings from the first black box, recovered hours after the crash, led prosecutors to believe that Lubitz locked the captain out of the cockpit and put the plane into a steep descent.
The 144 passengers on board, including two Australians, came from 18 different countries, Germanwings has said.
Lufthansa, which owns Germanwings, earlier declined to comment, pointing to the ongoing investigation.
The BEA, whose investigation runs in parallel to judicial probes, will issue a final report in about a year that may include recommendations on cockpit doors and the handling of pilots’ medical records by the airline industry.