Investigators carry boxes from the apartment of Germanwings airliner jet co-pilot Andreas Lubitz, in Duesseldorf, Germany, March 26, 2015. [Photo/IC]

"MAD SUICIDAL ACTION"

French Prime Minister Manuel Valls urged patience on Friday but said the German airline had an obligation to share all information on Lubitz with investigators.

"We must wait for the end of the inquiry. I am careful when there is a judicial inquiry, but everything points to a criminal, mad, suicidal action that we cannot comprehend," Valls told iTELE.

"It is up to this company to provide a maximum of information so that we can understand why this pilot committed this dreadful act."

Lubitz was described by acquaintances in his hometown of Montabaur in western Germany as a friendly but quiet man who learned to fly gliders at a local club before advancing to commercial aviation as a co-pilot at Germanwings in 2013.

"I got to know him, or I should say reacquainted with him, as a very nice, fun and polite young man," said Klaus Radke, the head of the local flight club where Lubitz received his first flying licence years ago. Radke said Lubitz had returned in the fall for a refresher course.

But a friend who met Lubitz six years ago and flew with him in gliding school, said he had become increasingly withdrawn over the past year.

Before Lubitz became a co-pilot in late 2013, the friend said the two had gone to movies and clubs together. But he noticed at two birthday parties they attended over the past year that he had retreated into a shell, speaking very little.

"Flying was his life," said the friend, who agreed to speak to Reuters about Lubitz's mental state on condition of anonymity. "He always used to be a quiet companion, but in the last year that got worse."

Police raided Lubitz's family home in Montabaur and his apartment in Duesseldorf on Thursday in a search for clues.

"We took a number of items with us and we are evaluating them now," said a spokesman for the Duesseldorf police.

He declined to comment on a Spiegel Online report that police had found evidence of psychiatric illness in the Duesseldorf flat.