Medical confidentiality should be relaxed for pilots following last year's Germanwings disaster, French investigators say.
Co-pilot Andreas Lubitz was urged by a doctor to attend a psychiatric hospital weeks before he crashed the plane on 24 March 2015, but his employer was never alerted, the investigators' final report says.
All 150 people on board died when Flight 9525 hit a mountain in the French Alps.
Investigators believed Lubitz brought down the plane deliberately.
He had been suffering from severe depression, they said, but doctors had been unable to disclose this.
The report, by the French Land Transport Accident Investigation Bureau (BEA), said confidentiality had to be balanced with the risk an individual might pose to public safety and that "clearer rules" were needed.
It was also critical of pilots being able to make self-declarations about their health, which allowed them to hide any illnesses.
A union that represents German pilots welcomed the recommendations as a "balanced package of measures", but it said strict rules on data protection needed to be developed in conjunction with criteria for suspending confidentiality rules.
The report pointed out that strict German laws on protecting confidentiality were balanced by provisions protecting anyone who acted to prevent an immediate danger.
Countries including Canada, Israel and Norway had specific laws on confidentiality for pilots.
Lubitz's medical visits in weeks leading up to crash
BEA investigation head Arnaud Desjardin said Lubitz had in December 2014 started to show symptoms that "could be compatible with a psychotic episode" but this information was not passed on to Germanwings.
The report also called for more stringent medical checks for pilots - it recommended regular analysis to check for "psychological or psychiatric problems".
But it has not suggested any change to cockpit rules. Lubitz was able to lock the pilot out of the cockpit while he crashed the plane, taking advantage of a system designed to prevent hijackings by attackers elsewhere on board.
"A lockage system cannot be created to prevent threats coming from both outside and inside the cockpit," Mr Desjardin said.
Many airlines now required at least two people to be in the cockpit at any given time.
Both Germanwings and its parent company Lufthansa had previously said that Lubitz, 27, had passed all tests of fitness to fly.
Lufthansa has acknowledged that it knew the co-pilot had suffered from severe depression in 2009 while training for his pilot's licence.