Motive examined after black box reveals co-pilot crashed deliberately

Investigators carry boxes from the apartment of Germanwings airliner jet co-pilot Andreas Lubitz, in Duesseldorf, Germany, March 26, 2015. [Photo/IC]

Setting the plane's controls for rapid descent was an act that "could only have been voluntary", Robin said. "He had... no reason to stop the pilot-in-command from coming back into the cockpit. He had no reason to refuse to answer to the air controller who was alerting him on the loss of altitude."

The captain, who had stepped out of the cockpit, probably to use the toilet, could be heard on flight recordings trying to force his way back in. "You can hear banging to try to smash the door down," Robin said.

Most of the passengers would not have been aware of their fate until the very end, he said: "Only towards the end do you hear screams," he said. "And bear in mind that death would have been instantaneous...the aircraft was literally smashed to bits."

FlightRadar24, an online air tracking service that uses satellite data, said it had found evidence the autopilot was abruptly switched from cruising altitude to just 100 feet, the lowest possible setting. The plane crashed at about 6,000 feet.

"Between 09:30:52 and 09:30:55 you can see that the autopilot was manually changed from 38,000 feet to 100 feet and 9 seconds later the aircraft started to descend, probably with the 'open descent' autopilot setting," Fredrik Lindahl, chief executive of the Swedish tracking service, said.

Spohr said its air crew were picked carefully and subjected to psychological vetting.

"No matter your safety regulations, no matter how high you set the bar, and we have incredibly high standards, there is no way to rule out such an event," Spohr said.

Attention was focused on the motivations of Lubitz, a German national who joined the Lufthansa-owned budget carrier in September 2013 and had just 630 hours of flying time - compared with the 6,000 hours of the flight captain.

"Suicide" was the wrong word to describe actions which killed so many other people, Robin, the French prosecutor, said: "I don't necessarily call it suicide when you have responsibility for 100 or so lives."

The family of the co-pilot, whose age was earlier misstated as 28, arrived in France for a tribute alongside other victims. They were being kept apart from the others, Robin said.

Acquaintances in the town said they were stunned.

"I'm just speechless. I don't have any explanation for this. Knowing Andreas, this is just inconceivable for me," said Peter Ruecker, a long-time member of the local flight club where Lubitz received his flying license years ago.