A French prosecutor on Thursday laid out the chilling details, based on a transcript of the final 30 minutes of a cockpit voice recorder, of how Germanwings co-pilot Andreas Lubitz intentionally flew an Airbus carrying 150 people into the Alps.
Brice Robin said at a news conference that for the first 20 minutes, the captain of the plane and Lubitz spoke in a cordial, normal fashion with each other and there was nothing unusual about the conversation.
After a flight attendant prepared for the flight's arrival in Düsseldorf, the pilot asked Lubitz to take control. There was a sound of a chair being pushed back and a door being closed, which indicated that the captain had left the cockpit to presumably use the restroom.
"At this point the co-pilot is the only one in the cockpit," Robin said. "So it's while he's alone that he has somehow manipulated the buttons on the flight monitoring system to accelerate the plane's descent. I repeat, he was alone at the helm of this plane."
Robin reiterated that the action of starting the aircraft's descent at that particular altitude could only be done deliberately and that it was not automatic.
The captain was then heard calling Lubitz to regain access into the cockpit using the internal communication system.
"We hear several cries of the pilot asking to access the cockpit," Robin said. "Through the intercom system, he identifies himself, but there is no answer; he knocks on the door, but receives no response from the co-pilot."
There were sounds of "normal breathing" from inside the cockpit up until the final point of impact, which indicated that Lubitz was alive. Air traffic controllers from a control tower in Marseille began asking for a distress signal, but when there was no response it meant that the flight became a priority compared to every other flight at that point, Robin said.
Alarm systems were triggered, indicating the proximity of the ground to everyone on board. Violent blows to break down the cockpit door were also heard, presumably by the captain trying to get back into the cockpit. But the door was reinforced, according to international security norms to protect against terrorist acts, Robin said.
The sound of the plane's first impact was heard, which meant it could have glanced or hit something before the final impact. No distress calls or mayday signals were made by the co-pilot despite several calls from the control tower.
"The most likely interpretation in our view is that the co-pilot, through deliberate abstention, refused to open the cockpit door to the chief pilot and used the button which controls loss of altitude," said Robin.
In the last eight minutes the aircraft went from 10,000 to 12,000 meters to virtually 2,000 meters. The mountain it hit was between 1,500 and 2,500 meters.
"He used this button to lose altitude for reasons that are totally unknown to us at the moment," said Robin, adding that his actions could be analyzed as "a deliberate attempt to destroy the aircraft."
Robin said the passengers became aware of what was going on only at the last moment because the aircraft was very large and the passengers were not near the cockpit.
"We hear screams only in the very last moments before the impact. The screams are in the last instance," he said.
"Death was instantaneous," Robin said, because the aircraft was going 700 kilometers an hour before hitting the mountain.