French prosecutors said that, according to evidence from the recovered cockpit voice recorder, co-pilot Andreas Lubitz, 28, had deliberately put the Germanwings plane into a descent after the captain had left the cockpit.
He then repeatedly refused to allow the captain back into the cockpit, with the captain being heard pounding on the door in a desperate attempt to break in.
Mr Lubitz had then failed to respond to any communication from the ground or from other aircraft in the vicinity. Breathing was heard coming from him right up until the moment of impact.
The recording also suggests the passengers were unaware of what was happening until the final moments, when their screams can be heard.
Marseille prosecutor Brice Robin said: “The most probable interpretation is that the co-pilot refused to open the cockpit door to the pilot and actioned the button which started the descent procedure.
“We can only deduce that it destroyed this plane.”
All 150 people on board, including three Britons, died in the crash last Tuesday.
Carsten Spohr, chief executive of Lufthansa, Germanwings’ parent company, said the incident was “beyond our worst nightmares”.
He said Mr Lubitz’s previous performance had been “without any criticism”.
The cockpit voice recording revelations led to the spotlight being thrown on the fact that Mr Lubitz’s training had been interrupted for a long period.
He had been employed as a flight attendant when he first tried to become a pilot in 2008 after waiting for eight months, but did not start working as a first officer for Lufthansa until September 2013.
Mr Spohr, said: “The co-pilot interrupted his training for six years, I would be interested to know why.
“I cannot tell you anything about the reasons of this interruption, but anybody who interrupts the training has to do a lot of tests so the competence and fitness would be checked again.”
Matthias Gebauer, chief correspondent for the online edition of German newspaper Der Spiegel, tweeted: “Schoolmates of co-pilot who crashed tell German reporters he took six-months break from flight training in 2009 due to burnout-syndrome.”
Mr Robin’s startling account of the plane’s final half hour showed that for the first 20 minutes the two pilots talked in a normal fashion and were as courteous as two pilots would be.
Mr Robin said the co-pilot’s responses, initially courteous, became “curt” when the captain began the mid-flight briefing on the planned landing.
The captain is then heard asking the co-pilot to take over and the sound of a chair being pushed back and a door being closed is heard. It was assumed that the captain had gone to the toilet, leaving the co-pilot in charge of the plane.
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Mr Robin went on: “The co-pilot uses the flight monitoring system to start the descent of the plane. This can only be done voluntarily, not automatically.
“We hear several cries from the captain asking to get in. Through the intercom system he identifies himself — but there is no answer. He knocks on the door and asks for it to be opened — but there is no answer.”
Mr Robin said that after entry to the cockpit was denied, the sound of breathing from inside the cockpit was heard and this sound carried on until the moment of impact.
“The co-pilot was still alive at this point,” Mr Robin said. He said there was no distress signal, no Mayday and no answer despite numerous calls to the plane from ground controllers.
The cockpit voice recorder also shows that there were alarm signals going off, indicating the proximity of the ground.
Speaking about whether the passengers realised what was happening, Mr Robin said: “I think the victims only realised at the last moment because on the recording we only hear the screams on the last moments of the recording.”
He added: “I believe that we owe the families the transparency of what the investigation is pointing to and what is going on, we owe it to them to tell them what happened.
“The families have been informed of everything I just told you.”
Asked about Mr Lubitz’s ethnicity, Mr Robin said: “He was a German national and I don’t know his ethnic background.
“He is not listed as a terrorist, if that is what you are insinuating.”
Pressed on the co-pilot’s religion, he said: “I don’t think this is where this lies. I don’t think we will get any answers there.” He said German authorities were taking charge of the investigation of Mr Lubitz.
In Cologne, Mr Spohr said, irrespective of all the sophisticated safety devices, “you can never exclude such an individual event”, adding “no system in the world could manage to do that”.
He added: “We can only speculate what might have been the motivation of the co-pilot. In a company that prides itself on its safety record, this is a shock. We select cockpit personnel carefully.”
Acquaintances in Mr Lubitz’s home town of Montabaur in western Germany said he was happy and showed no signs of depression when they last saw him. One described him as quiet but friendly.
Lufthansa chief executive Carsten Spohr reflected on his long experience as he reacted to news that the Germanwings crash that killed 150 had been blamed on the deliberate action of the co-pilot.
Mr Spohr told a news conference that “no system in the world can rule out such an isolated event”.
He added: “I have worked at Lufthansa as an engineer, I have worked as a pilot at Lufthansa, I have carried responsibility as a manager at Lufthansa for many, many years. Always, wherever I was, whoever my boss was, the rule was always safety is No 1. And that this has happened to us — I can only say we are sorry.”
Mr Spohr told a news conference in Cologne, Germany, that “we choose our staff very, very carefully”. He says the airline had no indication of why the co-pilot would have crashed the plane. He said pilots undergo yearly medical examination, but that doesn’t include psychological tests.
A Spanish factory worker, who lost two friends in the Germanwings crash, says he had “a feeling of impotence, of rage” after hearing that the disaster was blamed on deliberate actions by the plane’s co-pilot.
Esteban Rodriguez works for auto parts maker Delphi in Sant Cugat, a town of 85,000 near Barcelona. His friends, Rogelio Oficialdegui and Manuel Rives, were among 50 Spaniards who died in Tuesday’s crash, which killed 150 people.
Mr Rodriguez said: “One person can’t have the right to end the lives of hundreds of people and families.”
Spanish Prime Minister Mariano Rajoy says he was “shocked by the latest details provided by investigators”.
In a message on his official Twitter account, Mr Rajoy said that once again he sends “an emotional embrace to the families” of those who died in France.
The principal of Joseph Koenig High School in Haltern, Germany, which lost 16 students and two teachers in the Germanwings crash, says the state governor called him with news that the cause “was without a doubt suicide”.
Ulrich Wessel told reporters: “I gave this information to my colleagues immediately, and they were just as stunned as I was.
“I told them it is much, much worse than we had thought. It doesn’t make the number of dead any worse, but if it had been a technical defect then measures could have been taken so that it would never happen again,” he said.
“It is and remains important that further inquiries take place and that every aspect is further investigated,” German Chancelor Angela Merkel said.
“This is an unbearable tragedy … this information leaves us without words.
“What I want to say today is that this is a crime against all the victims and families involved,” she continued.
Mozambique Airlines Flight 470 was an international passenger Embraer 190 jet flying from Maputo International Airport.
During the flight, Captain Herminio dos Santos Fernandes manually changed its autopilot settings three times from 38,000 feet to 592 feet — which was below ground level — as well as adjusting the speed.
The cockpit voice recorder captured several alarms going off during the descent, as well as repeated loud bangs on the door from the co-pilot, who was locked out of the cockpit.
An investigation concluded Captain Fernandes had a “clear intention” to crash the jet, and had kept his co-pilot out of the cabin so he could do so.
The plane crashed into the Bwabwata National Park in Namibia, about half way between its departure and scheduled arrival airport.
All 27 passengers and six crew members were killed.