By Michael Nienaber

BERLIN (Reuters) - The co-pilot suspected of deliberately crashing an airliner, killing 150 people, had told his girlfriend he was planning a spectacular gesture so "everyone will know my name", a German daily said on Saturday.

The Bild newspaper published an interview with a woman who said she had had a relationship in 2014 with Andreas Lubitz, the man French prosecutors believe locked himself alone in the cockpit of the Germanwings Airbus on Tuesday and steered it into the French 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 the paper gave the pseudonym of Maria W.

"I didn't know what he meant by that at the time, but now it's obvious," she said. "He did it because he realised 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."

The woman also told Bild: "We always talked a lot about work and then he became a different person. He became upset about the conditions we worked under: too little money, fear of losing the contract, too much pressure."

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.

German officials said there would be a ceremony on April 17 in Cologne Cathedral attended by German Chancellor Angela Merkel and senior officials from other countries including France and Spain.

Also on Saturday, relatives of the Germanwings captain whom Lubitz locked out of the cockpit before the crash visited a memorial to the victims in the French Alps, while a special mass was held at the small cathedral in nearby Digne-les-Bains.

"OVERSTRESS SYMPTOMS"

German authorities said on Friday they had found torn-up sick notes showing the co-pilot had been suffering from an illness that should have grounded him on the day of the tragedy. Germanwings, the budget airline of the flag carrier Lufthansa, 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 officials as saying Lubitz had also sought treatment for vision problems that may have jeopardized his ability to work 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.

(Additional reporting by Georg Merziger, Maria Sheahan, Tom Käckenhoff, Ingrid Melander and Reuters television; Editing by Andrew Roche and Raissa Kasolowsky)