The co-pilot suspected of deliberately crashing a Germanwings airliner into the French Alps told his girlfriend he was planning a spectacular gesture so "everyone will know my name," a German newspaper said on Saturday.

The Bild newspaper published an interview with a woman who said she had had a relationship in 2014 with Lubitz, the man French prosecutors believe locked himself alone in the cockpit of the Germanwings Airbus on Tuesday and steered it into the Alps, killing all on board.

"When I heard about the crash, I remembered a sentence...he said: 'One day I'll do something that will change the system, and then everyone will know my name and remember it,'" said the woman, a flight attendant who was given the pseudonym of Maria W by the newspaper.

"I didn't know what he meant by that at the time, but now it's obvious," she said. "He did it because he realized that, due to his health problems, his big dream of working at Lufthansa, of a having job as a pilot, and as a pilot on long-distance flights, was nearly impossible."

"He never talked much about his illness, only that he was in psychiatric treatment," she told the paper, adding they finally broke up because she was afraid of him. "He would suddenly freak out in conversations and yell at me," she recalled. "At night he would wake up screaming 'we are crashing' because he had nightmares. He could be good at hiding what was really going on inside him."

A Lufthansa spokesman declined to comment. The company and its low-cost subsidiary Germanwings took out full-page advertisements in major German and French newspapers on Saturday, expressing "deepest mourning."

Lufthansa and Germanwings offered condolences to the friends and families of the passengers and crew and thanked the thousands of people in France, Spain and Germany it said had helped since the crash. Lufthansa has also offered to pay $54,000 in immediate financial assistance per passenger to relatives of the deceased, a spokeswoman told Reuters.

German authorities said on Friday they found torn-up sick notes showing Lubitz had been suffering from an illness that should have grounded him on the day of the tragedy. Germanwings has said he did not submit a sick note at the time.

German newspaper Welt am Sonntag quoted a senior investigator as saying the 27-year-old "was treated by several neurologists and psychiatrists," adding that a number of medications had been found in his Duesseldorf apartment.

Police also discovered personal notes that showed Lubitz suffered from "severe subjective overstress symptoms," he added.

The New York Times on Saturday quoted unnamed officials as saying Lubitz had also sought treatment for vision problems.

The Times, citing officials with knowledge of the investigation, reported that Lubitz "sought treatment for vision problems that may have jeopardized his ability to continue working as a pilot."

German state prosecutors and police spokesmen declined to comment on the media reports, adding there would be no official statements on the case before Monday.

Investigators have retrieved cockpit voice recordings from one of the plane's "black boxes," which they say show that Lubitz locked himself alone in the cockpit, as his fellow pilot desperately tried to break in, and caused the airliner to crash.

A chief French investigator said on Saturday it was too early to rule out other explanations for the crash.

"There is obviously a scenario that is well known to the media and which we are focusing on," French investigator General Jean-Pierre Michel told French media.

"But we have no right today to rule out other hypotheses, including the mechanical hypotheses, as long as we haven't proved that the plane had no (mechanical) problem," he added, pointing out that a second black box containing flight data had not been found yet.