A French prosecutor has said the co-pilot of a Germanwings flight that crashed in the Alps appeared to want to "destroy the plane".

Marseille prosecutor Brice Robin said the co-pilot was alone at the controls and "intentionally" sent the plane into the doomed descent.

Mr Robin said: "We hear the pilot ask the co-pilot to take control of the plane and we hear at the same time the sound of a seat moving backwards and the sound of a door closing.

"At that moment, the co-pilot is controlling the plane by himself. While he is alone, the co-pilot presses the buttons of the flight monitoring system to put into action the descent of the aeroplane.

"This action on the altitude controls can only be deliberate."

"The most plausible interpretation is that the co-pilot through a voluntary act had refused to open the cabin door to let the captain in. He pushed the button to trigger the aircraft to lose altitude. He operated this button for a reason we don't know yet, but it appears that the reason was to destroy this plane."

Mr Robin said that air traffic controllers made repeated attempts to contact the aircraft, but to no avail.

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EVIDENCE: The voice data recorder that was recovered from the crash site

He said pounding could be heard on the door during the final minutes before the crash as alarms sounded.

The co-pilot "voluntarily" refused to open the door and his breathing was normal throughout the final minutes of the flight, he said.

Mr Robin identified the pilot as a German national and who had never been flagged as a terrorist.

He said information has been pulled from the black box cockpit voice recorder but the co-pilot did not say a word once the captain left the cockpit. "It was absolute silence in the cockpit," he said.

Mr Robin named the co-pilot as Andreas Lubitz. In the German town of Montabaur, acquaintances said he was in his late 20s and showed no signs of depression when they saw him last autumn.

"He was happy he had the job with Germanwings and he was doing well," said a member of a glider club, Peter Ruecker, who watched him learn to fly. "He gave off a good feeling."

The Northern Echo:
CRASH SITE: The Germanwings plane crashed into the French Alps

Lubitz had obtained his glider pilot's license as a teenager and was accepted as a Lufthansa pilot trainee after finishing a tough German college preparatory school, Mr Ruecker said. He described Lubitz as a "rather quiet" but friendly young man.

The Airbus A320, on a flight from Barcelona to Duesseldorf, began to descend from cruising altitude after losing radio contact with ground control and slammed into the remote mountain on Tuesday morning, killing all 150 people on board.

Lufthansa has not identified the pilots but said the co-pilot joined Germanwings in September 2013, directly after training, and had flown 630 hours.

The captain had more than 6,000 hours of flying time and been a Germanwings pilot since May 2014, having previously flown for Lufthansa and Condor, Lufthansa said.