One year before he made the cut for Lufthansa's elite flying school, Andreas Lubitz worked at a Burger King behind a car wash, flipping Whoppers and frying fries and talking to co-workers about his dream.

One day, he told them, he would be a pilot.

That dream finally started to come together in 2008, when Lubitz would leave for Bremen, Germany, then travel to Phoenix, Arizona, to attend one of the industry's most rigorous commercial pilot-training programs. But by 2009, Lubitz had walked out of the program he had fought so hard to attend, taking several months off and coming back to his home town. During that hiatus, Detlef Adolf — general manager at the Burger King here and Lubitz's former boss — remembers his former employee stopping by the restaurant, buying a meal and sharing his distressing news.

"He had come back because he said the pressure was too great," Adolf said Saturday.

Investigators now believe that Lubitz, 27, deliberately flew an Airbus A320 with 150 people on board into a remote corner of the French Alps on Tuesday, provoking a search for answers that is increasingly centering on his health, and his mental health in particular.

The picture emerging of Lubitz is one of a man haunted, whose ambition to fly brought him both pleasure and torment. Authorities have found doctors' sick notes stating he was unfit for work, including on the day of the crash. On Saturday, Germany's Bild newspaper quoted an interview with a former girlfriend of Lubitz's who described a man who suffered from both vivid nightmares and delusions of grandeur.

"At night, he woke up and screamed: 'We're going down!' because he had nightmares," the former girlfriend told Bild. "He knew how to hide from other people what was really going on with him."

She added that last year he had warned, "One day I will do something that will change the whole system, and then everybody will know my name and remember it."

Bild and the New York Times reported on Saturday that Lubitz was seeking treatment for vision problems, though it remained unclear whether the issue was real or perhaps psychosomatic. Such concerns could have led Lubitz to worry that he would permanently lose his medical certification to fly.

Here in his home town in southwestern Germany, a city of 13,000 dotted with traditional houses and well-tended lawns centered on an aging Main Street, the mood shifted between denial and sorrow over its local boy made good. Yet Lubitz was hardly a forceful presence here, and those who knew him described him as friendly, even bland — a non-memorable man who yelled out "Guten Tag" to neighbors on his morning runs but was otherwise quiet and reserved.

andreas lubitz
(This picture circulating on the internet and social networks allegedly shows Andreas Lubitz, posing in front of the Golden Gate Bridge in California. Lubitz, the German young co-pilot of the doomed Germanwings flight appears to have "deliberately" crashed the plane into the French Alps after locking his captain out of the cockpit, but is not believed to be part of a terrorist plot, French officials said. - AFP PHOTO)

"He was inconspicuous, normal, nice," said Michael Dietrich, the pastor at the Luther Church in Montabaur who taught Lubitz's confirmation class.

But on the day Lubitz appeared to fly that Airbus into a chilly French mountainside, he was hiding a potentially deadly secret: a chronic medical condition that a doctor had determined was serious enough to keep him out of the sky.

Authorities would not reveal the exact nature of Lubitz's illness. But an official from the German prosecutor's office in Düsseldorf, speaking on the condition of anonymity because he was not authorized to reveal details beyond an official statement, said earlier that the doctors' notes were related to a "long-lasting condition." Asked whether they were also related to psychiatric problems, he said, "Read between the lines."

The comments came after Germany's Bild newspaper reported that Lubitz had been treated for at least one "serious depressive episode" so bad that he had to suspend flight training for several months in 2009. On Friday, the Rheinische Post also reported that the medical notes discovered in Lubitz's apartment came from at least two doctors — suggesting he may have been searching for a favorable diagnosis and possibly feared losing his medical certification to fly.

German aviation authorities said that Lubitz's medical file, tied to his pilot's license, contained a notation that he was required to have "special regular medical examinations," but such citations can relate to a wide range of medical conditions.

Yet the prospect that mental-health problems may have figured in the crash of the Germanwings plane additionally shined a spotlight on what critics call flaws in the regular medical checks required of airline pilots, who must pass as many as two exams per year. Such tests, however, are largely geared toward catching physical ailments, such as vision or heart problems, that could impair performance in a cockpit. But mental-health tests in fitness evaluations are often cursory, sometimes amounting to little more than a written questionnaire.

"Typically, there are no tests applied to identify psychological diseases," said Andreas Adrian, an aviation doctor who evaluates Lufthansa's and other airlines' pilots in Bremen, Germany. "Maybe you are giving someone a questionnaire to answer, but of course, you can get a good actor and he can easily hide any issues."

The debate intensified on Friday over whether mental health should be more deeply probed — an effort strongly opposed by some pilot groups and others who say such a policy could add to the pressures of an already high-stress job.

More rigorous mental-health testing could "uncover thousands of people who are going through difficult times in their lives and prevent them flying when they are perfectly capable of carrying out their normal day jobs," said Philip Baum, editor of the magazine Aviation Security International. "You will have to employ far more pilots, and it would be an additional stress and could make things worse."

The possibility that Lubitz may have hidden his condition — a task that could have been made easier by strict medical privacy laws in Germany — might help explain how he passed his flight training program. Lufthansa chief executive Carsten Spohr said this week that his company, which owns Germanwings, was never informed of the reason for Lubitz's medical leave in 2009, a period in which the newspaper Bild said Lubitz was suffering from clinical depression.

Yet, even if he did hide an illness, the fact that Lubitz — who lived here in Montabaur much of the year with his parents — passed muster at Lufthansa's demanding flight school with what Spohr called "flying colors" raised additional questions. The course is meant to weed out potentially troubled men and women, using role-play scenarios in cockpits to measure reactions to conflict and stress, as well as highly personal lines of questioning to assess psychological balance.

"They have to expect questions about their personal histories," said Michael Müller, chief executive of ATTC, a company that helps prepare pilot candidates for entering flight schools, including Lufthansa's. "How did you grow up? Did your parents divorce? How did you feel when they did?"

Under existing aviation laws, any diagnosis of depression or other serious mental illness should have made it difficult for Lubitz to continue flying in Europe, and certainly not without extensive treatment. Even then, certain limitations are placed on pilots who are taking psychotropic medications — such as popular anti-depressants — including a stipulation that they not be alone in the cockpit.

Investigators, meanwhile, sought more answers about the man who German and French investigators believe brought down Flight 9525 on his own.

At Lubitz's apartment in a leafy middle-class neighborhood on the outskirts of Düsseldorf, neighbors had affixed Germany's black, gold and red flag at half-staff on a utility pole. Pink camellias bloomed near the entrance to the three-story building, and a small palm tree sat on Lubitz's balcony.

On the doorbell, the name Goldbach appeared with Lubitz's. Neighbors said Goldbach was the last name of the woman who lived with Lubitz in the apartment. It was not immediately clear whether they were married.

Lubitz and Goldbach were both reserved but friendly, and Lubitz would from time to time walk along the street in his pilot's uniform, neighbors said, on at least one occasion stopping to play with a neighbor's 3-year-old daughter.

A police spokesman outside the building said Friday that investigators had completed their searches a day earlier, spending 3 1/2 hours scouring the apartment and taking away two cardboard boxes and a large bag of Lubitz's possessions.

The University Hospital Düsseldorf confirmed that Lubitz visited the facility in February and, for the last time, on March 10 for "diagnostic clarifications." The hospital statement gave no further details, citing medical confidentiality. But it denied German media reports that Lubitz had been treated there for depression.

Its psychiatric and neurologic clinic is a 10-minute drive from Lubitz's Düsseldorf home, on a rolling campus filled with Italianate buildings.