French air crash investigators have called on aviation authorities around the world to introduce new rules to allow doctors to sound the alarm about mentally ill pilots, loosening existing privacy laws.

The recommendations follow a year-long probe into the Germanwings crash, where co-pilot Andreas Lubitz, who had a history of depression, steered a plane into a mountain in the French Alps, killing 150 people.

The report by France’s BEA air accident investigation agency found that two weeks before the crash in March 2015 a doctor recommended hospitalising Lubitz because he showed signs of having a “psychotic episode”.

But this information “was not delivered to Germanwings” out of fear of breaching German privacy laws. According to the report, there was a “lack of clear guidelines” in Germany when a threat to public safety outweighed patient privacy.

“It is likely that breaching medical confidentiality was perceived by these doctors as presenting more risks, in particular for themselves, than not reporting the co-pilot to authorities,” it said.

Germanwings, the low-cost arm of Lufthansa that has rebranded to Eurowings since the crash, has come under scrutiny for allowing Lubitz to fly despite a known history of mental illness.

Lubitz had interrupted his initial Lufthansa training for several months because of psychological problems although he was allowed to return in 2009, having received the “all clear” from his doctors.

But the BEA report said that Germanwings could not be blamed because neither Lubitz nor his doctors informed them of his latest bout of mental illness and so “no action could have been taken . . . to prevent him from flying”.

His professional level was judged to be “above standard” by his flight instructors and examiners, according to the report, which said that none of his colleagues had “any concern” about his conduct before the crash.

The BEA recommended a range of other new safety measures, including support groups for aviation workers and a push to remove the stigma and fear of losing a job for those with mental health issues.

The BEA stopped short of mandating psychological tests every year for all pilots, saying it would be “neither effective nor beneficial”. It instead recommended tougher monitoring of pilots who have previously had issues.

Lufthansa pledged on Sunday to back the new safety recommendations, saying it will “continue to co-operate with the relevant authorities and will support the possible implementation of concrete measures”.

Lubitz was left alone at the controls of the Barcelona to Düsseldorf flight 30 minutes after take off and took the opportunity to lock the door and start an eight-minute descent into the ground. Flight recording data shows the second pilot was banging on the door to be let back in as the plane descended.

The BEA said that the cockpit door should still be allowed to be locked from the inside, however, as this was important to prevent outside attackers. “A lockage system cannot be created to prevent threats coming from outside and inside the cockpit,” it said.

Rémi Jouty, director of the BEA, said the report’s recommendations addressed weaknesses in the existing security measures, but that it was impossible to make them “100 per cent watertight”.

The BEA also said that Lubitz was using antidepressants Citalopram and Mirtazapine as well as the sleeping aid medication Zopiclone when he crashed.

A task force set up by the German government after the crash said last year that the “flow of information” between doctors and regulators in relation to the flightworthiness of pilots needed to be smoother.

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