Now the question is why. Authorities say there is no indication that this was a terrorist attack. Read more details below.
NYTimes PARIS — The chief Marseille prosecutor handling the investigation into the crash of a Germanwings jetliner said on Thursday that evidence from the cockpit voice recorder indicated that the co-pilot had deliberately locked the captain out of the cockpit and steered the plane into its fatal descent.
“At this moment, in light of investigation, the interpretation we can give at this time is that the co-pilot through voluntary abstention refused to open the door of the cockpit to the commander, and activated the button that commands the loss of altitude,” the prosecutor, Brice Robin, said.
He said it appeared that the intention of the co-pilot, identified as Andreas Lubitz, had been “to destroy the aircraft.” He said that the voice recorder showed that the co-pilot had been breathing until before the moment of impact, suggesting that he was conscious and deliberate in killing 144 passengers and five other crew members in the French Alps on Tuesday.
The inquiry had shown that the crash was intentional, Mr. Robin said, and he was considering changing his investigation from involuntary manslaughter to voluntary manslaughter.
He said there was no indication that this was a terrorist attack, and that Mr. Lubitz was not known to law enforcement officials. After the news conference, the German interior minister, Thomas de Maizière, told reporters in Berlin that security officials had checked their records after Tuesday’s crash and found no indication that anyone on board had links to terrorism.
An investigation into the background of Mr. Lubitz, who was 28 years old and came from the German town of Montabaur, is underway.
Asked if Mr. Lubitz had tried to commit suicide, he said, “I haven’t used the word suicide,” adding that it was “a legitimate question to ask.”
The revelation that one of the pilots of the jetliner was locked out of the cockpit before it crashed raised new and troubling questions on Thursday, as search teams continued to scour the rugged terrain of the French Alps for clues that could shed light on what happened. Several other issues remained unclear on Thursday, including the identity of the captain and why he had left the cockpit.
The flight, an Airbus A320 operated by the budget carrier Germanwings, was traveling to Düsseldorf, Germany, from Barcelona, Spain, on Tuesday morning when it descended and slammed into the French Alps.
The prosecutor said that the authorities had a full transcript of the final 30 minutes of the voice recorder.
“During the first 20 minutes, the pilots talk normally,” he said, saying they spoke in a “cheerful” and “courteous” way. “There is nothing abnormal happening,” he said.
The prosecutor said the transcript showed that the captain was preparing a briefing for landing in Düsseldorf. The co-pilot’s answer, the prosecutor said, was “laconic.”
The commanding pilot then asked the co-pilot to take over, and the noise of a seat backing up and a door closing could be heard.
“At this stage, the co-pilot is in control, alone,” the prosecutor said. “It is when he is alone that the co-pilot manipulates the flight monitoring system to activate the descent of the plane.” The prosecutor said that this action could only have been “voluntary.”
“You can hear the commanding pilot ask for access to the cockpit several times,” the prosecutor said. “He identifies himself, but the co-pilot does not provide any answer.”
“You can hear human breathing in the cockpit up until the moment of impact,” he said.
Before the plane crashed, he said, the sound of passengers screaming could be heard.
During the descent, he said, air traffic controllers repeatedly tried to contact the aircraft but received no response.
Martin Riecken, a spokesman in Frankfurt for Lufthansa, the parent company of Germanwings said before the news conference in Marseille that “both pilots had been trained to Lufthansa standards.”
A flight club based near Montabaur posted a death notice for “Andreas” on its website. “Andreas became a member of the club as a youth to fulfill his dream of flying,” the LSC Westerwald club said on its website.
“He fulfilled his dream, the dream he now paid so dearly with his life,” the club said.
The posting appeared on the site before Mr. Robin told reporters in Marseille that the co-pilot had consciously put the plane on course to land while flying over mountainous terrain with no airport in the region.
Mr. Lubitz was registered as living with his parents in the Montabaur region, but he also had a home in Düsseldorf, the German TV station N24 reported.
The news conference raised the possibility of a pilot suicide. The captain, who left the cockpit, would have had to have followed a precise procedure to get back in. Assuming the cockpit door did not malfunction, analysts said, it was possible that the co-pilot could have activated a switch that would have denied the captain access to the controls for several minutes.
In 1999, after a Cairo-bound EgyptAir flight crashed in the Atlantic Ocean off Nantucket, Mass., killing 217 people, investigators at the time said they suspected that the co-pilot might have attempted suicide. The United States National Transportation Safety Board, which was charged with the investigation, concluded that the crash had occurred because of the co-pilot’s “manipulation of the airplane controls,” although its report explicitly did not use the word suicide.
Stefan Schaffrath, an Airbus spokesman, said on Thursday that in the wake of the Sept. 11, 2001, terrorist attacks in the United States, Airbus had upgraded the reinforcements of cockpit doors on its planes in compliance with international regulations.
According to an Airbus video describing the operations of locking the cockpit door, it is locked by default when closed. But when a pilot wants to lock the cockpit door to bar access to someone outside, he or she can move the toggle to a position marked “locked,” which illuminates a red light on a numeric code pad outside. That disables the door, keypad and the door buzzer for five minutes.
While these functions are disabled, the video shows, the only way to make contact with the crew is via an intercom. The doors can then only be opened if someone inside overrides the lock command by moving and holding the toggle switch to the “unlock” position.
If someone outside the cockpit suspects the pilot is incapacitated, that person would normally first try to establish contact via the intercom or by activating a buzzer. If those efforts were unsuccessful, the video shows, a crew member outside the cockpit would need to enter an emergency code on the keypad.
The code activates a loud buzzer and flashing light on the cockpit control panel, and it sets off a timer that unlocks the door 30 seconds later. The person outside has five seconds to enter before the door locks again.
Dominique Fouda, a spokesman for the European Aviation Safety Agency in Cologne, said that there was no regulatory requirement in Europe for a cabin crew member to be present in the cockpit when one of the pilots leaves for “physiological reasons.”
“Basically, unless they have a physiological need, they have to be in the cockpit,” he said.
Aviation safety experts said that the standards in the United States were similar, although Laura Brown, a spokeswoman for the Federal Aviation Administration in Washington, said she could not immediately confirm this.
As investigators continued to pore over the clues, relatives of the victims were expected to arrive on Thursday near the site of the crash, where a makeshift chapel has been set up, and where psychologists are available to provide support. Lufthansa was to operate two special flights for family members on Thursday from Barcelona and from Düsseldorf.
The victims of the crash included many Germans and Spaniards, including 16 high school students who were returning from an exchange program. Other victims included citizens of Britain, Colombia, Iran, Israel and the United States, among others.
A charter flight with 62 relatives and friends of victims landed in Marseille on Thursday after leaving Barcelona shortly after 10 a.m., Spanish television reported. Other relatives traveled by bus overnight from Barcelona, although their number was unconfirmed. All were expected to be driven to near the crash site, under the supervision of psychologists and other medical staff members.
The Spanish government announced Thursday morning that 50 victims were now believed to be Spaniards, down from 51 on Wednesday. One of the victims lived in Spain but did not have Spanish citizenship.
Because of an editing error, an earlier version of this article and an email news alert misstated the day that the chief Marseille prosecutor discussed the co-pilot’s actions. It was Thursday, not Tuesday.
An earlier version of the above correction omitted the source of the error. It was made during the editing process, not by the reporters.