DUESSELDORF, Germany (AP) — How could someone once diagnosed with suicidal tendencies get a job as a commercial pilot, entrusted with the lives of hundreds of people? That’s the question being asked after officials confirmed Monday that Germanwings co-pilot Andreas Lubitz received lengthy psychotherapy before receiving his pilot’s license.

All 150 people on board were killed by what prosecutors believe was a deliberate decision by Lubitz to slam the Airbus A320 he was flying from Barcelona to Duesseldorf into a mountain in the French Alps last Tuesday.

Lufthansa, Germanwings’ parent company, declined to say whether it knew of Lubitz’s mental health problems. But it said the young pilot had passed all required medical checks since starting work for its subsidiary two years ago.

Prosecutors in Duesseldorf, where Lubitz had an apartment, said the psychotherapy occurred over an extended period before he received his pilot’s license, and that medical records referred to “suicidal tendencies.” They provided no dates.

Lubitz started pilot training in 2008, though it’s unclear when he finished the at least three-year-long course and received his license. Lufthansa said he was certified to fly its aircraft in 2013.

The country’s aviation authority wouldn’t comment on Lubitz’s health, despite acknowledging last week that his record with the agency noted he needed “specific regular medical examination” beyond the annual checkup required of all pilots.

“The German Federal Aviation Office isn’t directly responsible for assessing the air-medical fitness of pilots,” said Cornelia Cramer, a spokeswoman for the agency, which is in charge of granting pilots’ licenses.

Cramer said the medical checks are conducted by specially trained doctors, but declined to say whether their findings are passed on to the agency.

The head of the German Aviation Medical Practitioners Association, the organization representing doctors who determine if pilots are medically fit to fly, said the standard medical evaluation would not have been able to determine if a pilot suffered from a serious mental illness.

All pilots must undergo regular medical checks that include a cursory psychological evaluation, according to Dr. Hans-Werner Teichmueller, the agency’s head. But such tests rely on patients being honest with their doctors, and even a seriously mentally unstable person would have been able to put a “mask” on for the investigation, he said.

“You can’t see anything beyond the face,” Teichmueller said. “We have developed a very refined system in Europe and most of us are in agreement that this system is optimal. If we were to add more psychological tests or modify the way we test, then we can still not change a situation like this.”

Lubitz continued to visit doctors until recently, receiving notes that excused him from work — including for the day of the crash — but none referred to suicidal tendencies or aggression toward others, said prosecutors’ spokesman Ralf Herrenbrueck.

He didn’t say what medical help Lubitz was seeking at the time of the crash, but noted that there was no evidence of any physical illness.

While Lubitz was physically fit — he was an avid runner who took part in half-marathons — his future employers had at least some indication there was a problem.

Last week, Carsten Spohr, the CEO of Lufthansa, acknowledged there had been a “several-month” gap in Lubitz’s training six years ago, but refused to elaborate. Following the disruption, he said, Lubitz “not only passed all medical tests but also his flight training, all flying tests and checks.”

Prosecutors said they have so far found no indications in Lubitz’s family, his personal surroundings or in his work environment of any motive that might have prompted his actions. They found no evidence that he told anyone, be it family, friends or doctors, what he was going to do.

The case has prompted a debate in Germany about the country’s strict patient privacy rules. Doctors risk prison if they disclose information about their patients to anyone unless there is evidence they intend to commit a serious crime or harm themselves.

The head of the German Medical Association, Dr. Frank-Ulrich Montgomery, warned against hasty changes to the rules, saying that each case should be judged individually.

He noted that doctors can already notify authorities if, for example, a professional driver is an alcoholic.

At the crash site in the French Alps, meanwhile, authorities were poring over DNA evidence that has been painstakingly collected from the debris of Flight 9525, scattered across the steep mountainside. Authorities have identified 78 sets of DNA so far, according to the Marseille prosecutor’s office, as they strive to identify all the victims for the grieving relatives who have poured into France by the hundreds.

Workers with backhoes and tractors were laying down a road just over a mile (2 kilometers) long Monday to reach the remote crash site to help speed the investigation. Until now, recovery crews have had to helicopter in and be tethered to local mountaineers to avoid slipping down the rocky, unstable slope.

France has deployed some 500 gendarmes and emergency workers to secure the crash site, search for human remains, examine evidence and help the traumatized relatives.

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Jordans contributed from Berlin. Lori Hinnant in Marseille, Geir Moulson in Berlin and Jona Kallgren in Duesseldorf contributed to this report.