A private doctor recommended that the German pilot who crashed a Germanwings jet into the Alps last year should be treated in a psychiatric hospital two weeks before the disaster, French investigators said on Sunday publishing their final report on the crash.
All 150 people on board travelling between Barcelona and Duesseldorf died as a result of the Germanwings crash a year ago.
Prosecutors claimed co-pilot Andreas Lubitz, who had a record of severe depression, barricaded himself into the cockpit and deliberately ploughed the Airbus jet into a mountainside on March 24.
France's BEA air accident investigation office said in its final report that Lubitz had begun to indicate symptoms that could be consistent with a psychotic depressive episode in December 2014 and consulted several doctors over the following months, none of whom alerted aviation authorities or his employer.
BEA chief Remi Jouty said the French investigation had sought to identify the "systematic failures which led to this accident". The investigators had also looked at the "balance between medical secrecy and flight security."
Prosecutors have found evidence that the co-pilot, who also had eyesight problems and may have feared losing his job, had researched suicide methods and concealed his illness from his employer, sparking a debate on supervision and medical secrecy.
A German lawyer for some of the families of the dead said this month they intended to sue the training school in Phoenix, Arizona, which Lubitz attended, claiming it should have reported his psychological problems.
"The co-pilot interrupted his training there for a while due to psychological problems," lawyer Christof Wellens said. "He shouldn't have been allowed to resume his training."
During the flight on March 24, 2015, co-pilot Andreas Lubitz locked the pilot out of the cockpit. Ten minutes later the Airbus 320 crashed into a mountain hillside, killing all 144 passengers and six crew.