Germanwings co-pilot Andreas Lubitz was urged to see doctors at a psychiatric hospital two weeks before the crash in the French Alps, which killed 150 people, a final report has said.
Mr Lubitz locked his colleague out of the cockpit and purposefully crashed the plane in March 2015.
French accident investigation agency BEA recommended more medical checks for pilots as it published its findings.
French accident investigation agency BEA has recommended more medical checks for pilots following its investigation into the Germanwings crash in March 2015.
The announcement comes after it was revealed pilot Andreas Lubitz, who deliberately flew the aircraft into the French Alps, was told to seek psychiatric treatment just two weeks before.
A doctor said Lubitz, who died alongside 150 passengers, should be treated at a psychiatric hospital before the crash on 24 March.
BEA Director Remi Jouty said Lubitz began showing 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.
Families of the victims were previously Lubitz had seen 41 doctors in recent years but under German law none was able to alert his employers to his state of mind.
The BEA said because Lubitz had not informed anyone about the doctors' warnings, "no action could have been taken by the authorities or his employer to prevent him from flying".
About 800 people attended the commemoration that included a private ceremony and a minute's silence near the site of the crash.
Investigators found evidence co-pilot Andreas Lubitz deliberately flew the plane into a mountainside, killing 150 people.