• Pilot deliberately locked out of cockpit
• Co-pilot identified as German national Andreas Lubitz
• Conversation went from courteous to 'curt'
• Lubitz deliberately began fatal descent of plane
• 28-year-old refused to open door despite pilot's cries
• Lubitz was conscious until the moment of impact
• Black box recorded passengers screaming
The co-pilot of Germanwings flight A320 is believed to have deliberately crashed the plane carrying 150 people into the French Alps.
There were no survivors when the Airbus suddenly plummeted near Digne on a flight from Barcelona to Dusseldorf on Tuesday morning.
At a press conference on Thursday, Marseille Prosecutor Brice Robin revealed chilling details of the audio from one of the retrieved black box recorders.
He confirmed earlier reports that the pilot had been locked out of the cockpit after excusing himself momentarily, possibly to visit the bathroom.
The conversation between the two men previously had been "normal" and "courteous", but the co-pilot's responses turned "curt" when the captain began the mid-flight briefing.
While the co-pilot was alone he locked the door and engaged a flight-monitoring system which began the fatal descent of the plane, Robin said.
Identifying the co-pilot as a German national, Andreas Lubitz, aged 28, he added: “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."
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Lubitz “didn’t say a single” word while he was alone and could be heard breathing "normally" during the descent, he said.
Robin added: "It wasn't the breath of someone who was struggling. He didn't say a single word, it was total silence.
"We hear the breathing inside the cockpit and we hear it until the moment of impact.
"I think the victims only realised at the last moment because on the recording you only hear the screams on the last moment."
He added that there was no answer from the cockpit to communication with ground controllers or from other aircraft in the area.
At this point alarm systems were sounding on the plane informing those onboard of the aircraft's proximity to the ground.
Robin surmised: "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 deduct that it destroyed this plane."
When asked if Lubitz had committed suicide, Robin replied: "No, I'm not even going to mention this word because I don't know."
When pressed on Lubitz's religion, Robin said: "I don't think this is where this lies. I don't think we will get any answers there.
"He is not listed as a terrorist, if that is what you are insinuating."
"Not in our worst nightmare could we imagine something like this happening," said Germanwings following the description of the French Alps crash plane's last moments.
Lufthansa CEO Carsten Spohr said that there is no rule for the airline that if a pilot leaves the cockpit, they must be replaced by a memeber of the cabin crew - a practice used by US airlines. Spohr said he didn't know of any European airline that has that rule.
Speaking at a press conference in Cologne, Spohr said that Lubitz had broken off his training six years ago for several months, but that this was not unusual. He added that all pilots were subject 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," Reuters reported Spohr as saying.
Libutz was a member of a flying club called LSC Westerwald.
The club posted a tribute on its website, that said: "As a youth, Andreas became a member of the society. He wanted to realise his dream of flying.
"He was able to fulfill his dream, the dream that cost him his life."
The statement continued: "We mourn Andreas and the other 149 victims of the catastrophe. Our thoughts are with the families.
"We will not forget Andreas."
The message added he had been a member of the club since he was a youth and had learned to fly there.