Lufthansa chief Carsten Spohr refused to answer questions about his company's handling of the co-pilot responsible for the Airbus A320 French Alps crash which killed 150 people.

Mr Spohr visited the site of the Germanwings crash with Germanwings managing director Thomas Winkelmann but after making a statement, walked away and refused to answer shouted questions from the media about co-pilot Andreas Lubitz, who deliberately flew the plane into mountains.

Spohr thanked the rescue teams and the investigators and said Lufthansa, which is Germanwings' parent company, would continue to support the victims' families and help restore the crash site, adding that finding answers to the crash would take some time.

"We are just very very sorry that such a terrible accident could have happened in Lufthansa.

"We are learning more every day about the cause of the accident, but I think it will take a long long time for everybody, all of us, to understand how this could happen," he told reporters.

Reporters wanted Spohr to talk further about the fact that Lufthansa said it knew six years ago that Lubitz suffered from a "serious depressive episode".

The airline said that as part of its internal research it found emails Lubitz sent to the Lufthansa flight school in Bremen when he resumed his training there after an interruption of several months.

In them, he told the school he had suffered a "serious depressive episode", which had since subsided.

The airline said Lubitz subsequently passed all medical checks and it has provided the documents to prosecutors.

Meanwhile, Lufthansa has questioned the existence of a video of the last moments on the doomed plane reported to has been found on a mobile phone memory card at the crash site.

A spokesman for the company said: "We have not seen the video and we do not know if it exists. Therefore we cannot confirm if the video is genuine.

"Considering that everything on the plane was destroyed, it would be unusual for a mobile phone to survive the impact."