Investigators into last year’s Germanwings disaster have called for more stringent medical checks for pilots and for medical confidentiality to be relaxed.
But their final report, published on Sunday, has not recommended changes to rules to prevent pilots from locking the cockpit door from the inside.
Investigators believe co-pilot Andreas Lubitz deliberately brought down Flight 9525 in the French Alps on March 24, killing all 150 on board.
Lubitz had locked the Captain out of the cockpit using a system put in place to prevent hijackings or terror attacks.
The report said it was not possible to create a locking system to stop threats coming from both outside and inside the cockpit.
Since the disaster, many airlines now require that at least two people remain in the cockpit at all times.
The report by the BEA investigation agency said Lubitz had been suffering from severe depression and, in the weeks leading up to the crash, had been referred for psychiatric hospital treatment.
But, due to patient confidentiality, his employer had not been informed.
The report said clearer rules were needed and that confidentiality needs to be balanced with the risk posed to public safety.
It was also critical of pilots being able to make self-declarations about their health, which effectively allows them to hide any illnesses.
Germanwings parent Lufthansa Group has already acknowledged it knew Lubitz had suffered from severe depression in 2009 while training for his pilot’s licence.