THE co-pilot of the Airbus A320 which crashed in the French Alps appeared to want to 'destroy the plane', according to French prosecutors.

Andreas Lubitz put the plane into a descent after the captain had left the cockpit, Marseille prosecutor Brice Robin told reporters.

Evidence from the black box flight recorder suggests he then refused to open the cockpit door to the captain.

The captain knocked on the door and asked to be let in and there was no answer from the co-pilot. Later there are the sounds of attempts to break down the door, the prosecutor said.

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The prosecutor said the cockpit voice recorder gave information from the first 30 minutes of the flight.

For the first 20 minutes the two pilots talked in a normal fashion and were as courteous as two normal pilots would be.

Then the captain is heard asking the co-pilot to take over and the sound of a chair being pushed back and a door being closed is heard.

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."

Mr Robin said black box recordings showed that Mr Lubitz "was breathing normally, it wasn't the breathing of someone who was struggling".

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."

It was assumed that the captain had gone to the toilet, leaving the co-pilot in charge of the plane, the prosecutor said.

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."