Germanwings crash: Co-pilot Andreas Lubitz's intention "was to destroy the plane."

Chilling revelations from the Public Prosecutor of Marseille have revealed that the co-pilot of Germanwings flight 4U9525 deliberately crashed the plane.

The beginning of the flight was normal. Not a single passenger would have been aware of the intentions of the man who held their lives in his grip.

Related content: Who was Germanwings co-pilot Andreas Lubitz?

Passengers would have been immersed in the plane’s entertainment system, prodding at their IPhones or reading their kindles. Naive that they were safe cocooned in the hum of the cabin.

Most never giving a second thought to the two men in control of the plane.

It was only in the last few minutes that screams were heard. Death was instant.

The French prosecutor today has shed new, terrifying light on what happened on that flight.

Brice Robin, Public Prosecutor of Marseille, said at a news conference that the 28-year old German co-pilot of the Germanwings A320, Andreas Lubitz, “deliberately” brought the plane down after locking the captain out of the cabin.

The 30-minute cockpit voice recording retrieved from the black box “clearly” suggests that Andreas Lubitz “profited from the captain’s absence” after he left the cockpit to go to the toilet.

He ignored the increasingly anguished attempts of the captain to get back in.

But then the horror of the situation suddenly became clear. “The intention was to destroy the plane,” Robin said, speaking mostly in French.

Robin said there is audio of the co-pilot breathing, and that breathing continues until the moment.

“He (co-pilot) was alive until impact,” said Robin ruling out a theory that Andreas Lubitz had lost consciousness.

He told a press conference that the flight started normally with “jovial exchanges in German.”

“But when we hear the captain discuss the landing check list, the co-pilot’s response appears laconic. We hear the captain ask the copilot to take control, then we hear the noise of a seat that goes back and a door open, we can assume he went to relieve himself.”

“The co-pilot was alone. It is it this moment that he turns the buttons of flight monitoring system to action the descent of the plane.

“The action of this selectioner of altitude can only be deliberate,” he said.

When the captain returns, he tries to speak to the co-pilot via a visual intercom system, but got “no response from the copilot”.

“He taps on door, no response from the copilot” he said.

Air traffic control repeatedly tried to communicate with him, and asked other nearby planes to do so, to no avail. He sent no distress messages.

Alarms sounded to signal to crew the proximity of the ground. “Then we hear banging of someone trying to break down the door,” he said.

Desperate banging.

The alarm to pull the plane up then goes off.

“We only hear screams in the last seconds. Death was instant.”

149 people, including two Australians – a mother and adult son died.

Who was Andreas Lubitz?

As these terrifying details become clear details are emerging about co-pilot Andreas Lubitz.

He had been with Germanwings since September 2013 and had completed 630 hours of flight time.

Carsten Spohr, the head of Lufthansa, the German carrier that owns Germanwings told media that Lubitz had passed his medical and psychological tests “with flying colours.”

Spohr said Andreas Lubitz’s training had been interrupted briefly six years ago but was resumed after “the suitability of the candidate was re-established”.

News Limited reports that a Spiegel reporter, Matthias Gebauer tweeted that friend of Lubitz said he had “burnout or depression” in 2009 during this break.

Lubitz lived with his parents in Montabaur and also kept an apartment in Dusseldorf.

 Was it suicide?

When Mr. Spohr was asked whether the co-pilot had committed suicide, he replied. “I am not a legal expert.” He then added, “But when one person is responsible for 150 lives, it is more than suicide.”

French Interior Minister Thomas de Maiziere said that investigators are focused on Lubitz’ background and motives, though they have started to rule out any connection to a larger plot.

“There is no evidence of any kind terrorist background,” de Maiziere said in a statement.

The scenario has terrifyingly similar aspects to a 1999, Cairo-bound EgyptAir flight crash off Massachusetts. That flight killed 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.

How can the pilot be locked out?

On the Airbus, like virtually every other commercial passenger jet since the terrorist attack of 9/11 the pilot has control of the cockpit and the ultimate override power to prevent others from entering from the plane’s cabin.

Aviation consultant Chesley Sullenberger told CBS News that in the U.S., there are protocols in place which require there to be at least two members of the flight crew in the cabin at all times. If the pilot or co-pilot needs to leave for any reason – such as to visit the bathroom – a member of the cabin crew will step into the cockpit.

In Europe however there is no such requirement.

Sullenberger said commercial pilots are some of the most heavily scrutinized professionals in the world, but in the end, it is “very difficult to predict who is going to act in a very bizarre and harmful way.”

Fairfax Media asked Qantas and Virgin about Australian requirments – as it is understood that the Civil Aviation Safety Authority does not require a second person in the cockpit at all times.

Virgin said the airline would not comment on its safety and security policies.

Aviation sources, according to Fairfax Media Qantas does not require a second person in the flight deck at all times. A Qantas spokesman said “the airline had multi-layered systems in place to protect the flight deck.”

Passengers would have heard the pilot’s desperate attempt to knock down the door.

And in an answer which we all did not want to hear Aviation consultant Chesley Sullenberger said that given the nature of the panic at the cockpit door, the 144 passengers on the jet would have known what was going on.

“It would have been a terrifying number of minutes,” he said.

A niece of one of the victims from Belgium told RTL Radio that was a relief that the passengers were unaware of their impending demise until the final seconds, according to the black box voice recording.

“You can hear screams, but they didn’t live through eight minutes of total horror,”

For the families of the 149 passengers these revelations begin to provide answers – but also open up the doors to many darker questions.

“When you commit suicide, you die alone,” Prosecutor Brice Robin said in response to a question. “With 150 on the plane, I wouldn’t call that suicide.”

 Related content: Who was Germanwings co-pilot Andreas Lubitz?