A screen grab taken from an AFP TV video on March 24, 2015 shows debris at the crash site of a Germanwings Airbus A320 in the French Alps. (AFP Photo)
The co-pilot "voluntarily" initiated the descent of the Germanwings flight that crashed into the French Alps on Tuesday and refused to open the door to the pilot who was outside the cockpit, the lead investigator said on Thursday.
150 people died in the crash.
"The co-pilot is alone at the controls," said prosecutor Brice Robin, recounting information gathered from the "black box" recorder. "He voluntarily refused to open the door of the cockpit to the pilot and voluntarily began the descent of the plane."
The co-pilot was identified as Andreas Lubitz, 28, a German citizen who was "not known by us" to have any links to terrorism or extremists, the prosecutor said, adding that German authorities were expected to provide additional information on his background and private life soon.
The New York Times reported today that cockpit voice recordings showed one of the pilots left the cockpit and could not get back in before the plane went down, killing everyone onboard, The recordings did not make clear why the pilot left the cockpit or why he could not regain entry as the plane steadily descended toward a mountain range in a remote area of the French Alpine region.
Investigators were studying the voice recordings from one of the "black boxes" for answers on Thursday while the search continued for a second black box.
"The guy outside is knocking lightly on the door and there is no answer," an unnamed investigator told the Times, citing the recordings. "And then he hits the door stronger and no answer. There is never an answer."
"You can hear he is trying to smash the door down," the investigator added.
France's BEA air incident investigation bureau was not immediately available for comment on the Times report but earlier had said it was too early to draw meaningful conclusions on why the plane went down.
"We have just been able to extract a useable audio data file," BEA director Remi Jouty told a news conference at the agency's headquarters outside Paris.
Although he said "words" had been heard on the tape, Jouty would not confirm whether that meant the Airbus A320's pilots were conscious and he gave no details of the recordings.
The BEA said the plane started descending a minute after reaching cruising height and lost altitude for over nine minutes. The last words of the pilot to the ground confirmed the next navigational waypoint, ending with a call-sign and "thank you".
The New York Times quoted a senior military official involved in the investigation as saying the cockpit audio showed "very smooth, very cool" conversation between the pilots in the early part of the flight. The audio then indicated one of the pilots left the cockpit.
"We don't know yet the reason why one of the guys went out," the official added. "But what is sure is that at the very end of the flight, the other pilot is alone and does not open the door."
The Lufthansa spokesman said that since the September 11, 2001, hijacked plane attacks on the United States, cockpit doors cannot be opened from the outside, in line with regulations.
Interior Minister Bernard Cazeneuve earlier said a terror attack was not the main hypothesis. Jouty said, however, that no theory could be excluded yet.
While stressing it was too early to form a clear picture, he ruled out a mid-air explosion and said the crash scenario did not appear to be linked to depressurisation.
Among the new details, he said the airliner had flown in a straight line directly into the mountain, but would not say whether that seemed to be at the hand of a pilot or auto-pilot.
Police and forensic teams on foot and in helicopters investigated the crash site about 100 km (65 miles) north of Nice.
"When we go to a crash site we expect to find part of the fuselage. But here we see nothing at all," pilot Xavier Roy, coordinating air operations, said of the confetti of debris.
Roy said teams of investigators had been dropped by helicopter onto the site and were working roped together at altitudes of around 2,000 meters (6,000 feet).