The captain of a passenger jet that investigators believe was deliberately crashed into the French Alps, killing all 150 aboard, shouted at the co-pilot to "open the damn door" as he made desperate attempts to return to the locked cockpit, according to a German newspaper Sunday.

French officials say the plane's black box voice recorder indicates that Andreas Lubitz, 27, locked the captain out of the cockpit of the Germanwings jet and deliberately flew Flight 4U 9525 into a mountainside.

They believe that the more senior pilot tried desperately to reopen the door during the flight's eight-minute descent after he left to use the bathroom.

Germany's mass-circulation Bild on Sunday reported that data from the cockpit recorder showed that the captain shouted: "For God's sake, open the door", as passengers' screams could be heard in the background, moments before the fatal crash.

The pilot could then be heard trying to smash the door down with an axe, and then screaming to a silent Lubitz to "open the damn door".

Bild said that before leaving the cockpit the captain could be heard explaining to his colleague that he had not had time to go to the toilet before they left Barcelona.

German prosecutors believe Lubitz hid an illness from his airline but have not specified the ailment, and said he had apparently been written off sick on the day the Airbus crashed on its route from Barcelona to Duesseldorf.

As investigators race to build up a picture of Lubitz and any possible motives, media reports emerged saying he had suffered from vision problems, adding to earlier reports he was severely depressed.

Lubitz's ex-girlfriend, identified only as Maria W, told Bild Lubitz had told her: "One day I'm going to do something that will change the whole system, and everyone will know my name and remember."

"I never knew what he meant by that but now it makes sense," it quoted the "shocked" flight attendant as saying Saturday.


'Health problems'


Bild, which showed a photo of the ex-girlfriend from behind to conceal her face, said she had flown with Lubitz on European flights for five months last year and that he had had another girlfriend since her.

She said he could be "sweet" and would give her flowers but got agitated talking about work conditions, such as pay or the pressure of the job, and was plagued by nightmares. "At night he woke up and screamed 'We're going down!'," she recalled.

If Lubitz did deliberately crash the plane, it was "because he understood that because of his health problems, his big dream of a job at Lufthansa, of a job as captain and as a long-haul pilot was practically impossible", she told Bild.

She split up with him because it became "increasingly clear that he had problems", she said.

German police found a number "of medicines for the treatment of psychological illness" during a search at his Duesseldorf home, newspaper Welt am Sonntag weekly said, quoting an unnamed high-ranking investigator as saying he'd been treated by several neurologists and psychiatrists.

Sunday's Bild weekly and the New York Times, which cited two officials with knowledge of the investigation, said Lubitz had sought treatment for problems with his sight.


'Alone in cockpit'


Germanwings pilot Frank Woiton was quoted in Saturday's edition of Bild as saying he had flown with Lubitz, who had spoken about his ambitions to become a captain and fly long-distance routes.

He told the newspaper Lubitz handled the plane well and "therefore I also left him alone in the cockpit to go to the toilet".

French police investigator Jean-Pierre Michel told AFP that Lubitz's personality was a "serious lead" in the inquiry but not the only one.

The investigation has so far not turned up a "particular element" in the co-pilot's life which could explain his alleged action in the ill-fated Airbus plane, he said.

German prosecutors revealed that searches of Lubitz's homes netted "medical documents that suggest an existing illness and appropriate medical treatment", including "torn-up and current sick leave notes, among them one covering the day of the crash".

Lufthansa CEO Carsten Spohr has said that Lubitz had suspended his pilot training, which began in 2008, "for a certain period", before restarting and qualifying for the Airbus A320 in 2013.

The second-in-command had passed all psychological tests required for training, he told reporters.


National ceremony


Germany is to hold a national memorial ceremony and service on April 17 for the victims of Tuesday's disaster, half of whom were German, with Spain accounting for at least 50 and the remainder composed of more than a dozen other nationalities.

Around 500 people earlier Saturday attended a religious ceremony in the French town of Digne-les-Bains, about 40 kilometres (25 miles) south of the remote Alpine crash zone where searchers are recovering the victims' remains and evidence.

Candles for each of the victims were placed in front of the cathedral's altar.