The Germanwings co-pilot who caused the crash which killed 150 people was referred to a psychiatric clinic two weeks before the the tragedy, it has been revealed.
French air accident investigators recommended on Sunday that world aviation bodies draw up new rules requiring medical workers to warn authorities when a pilot's mental health could threaten public safety.
Co-pilot Andreas Lubitz had been treated for depression in the past, and the investigation found that he had consulted dozens of doctors in the weeks before the crash on 24 March last year.
But the many doctors didn't inform authorities of concerns about his mental health, France's BEA investigation agency said. One doctor referred Lubitz to a psychiatric clinic just two weeks before the crash, it said in its report on the disaster, according to the Associated Press.
"Experts found that the symptoms (he was presenting at that time) could be compatible with a psychotic episode," said Arnaud Desjardin, leader of the BEA investigation. This information "was not delivered to Germanwings."
Because Lubitz didn't inform anyone of his doctors' warnings, the BEA said, "no action could have been taken by the authorities or his employer to prevent him from flying."
Germanwings and parent company Lufthansa have strongly denied any wrongdoing in the crash, insisting that the 27-year-old was certified fit to fly.
But relatives of those killed have pointed to a string of people they say could have raised the alarm and stopped Lubitz, going back to the days when he began training as a pilot in 2008.
Flight 9525 from Barcelona to Dusseldorf crashed in the French Alps on March 24 last year, killing 150 people, and a probe found evidence suggesting co-pilot Andreas Lubitz deliberately downed the plane after locking the pilot out of the cockpit.
Philip Bramley's son Paul, 28, died along with two other Britons - Martyn Matthews, 50, from Wolverhampton, and seven-month-old Julian Pracz-Bandres, from Manchester, who died alongside his mother, Spanish-born Marina Bandres Lopez-Belio, 37.
Bramley, 60, from Hull, told the Sunday Mirror that if one of the 41 doctors who had seen him had reported their concerns, his son "would still be alive".
He said: "But it's my view that the airline is at fault.
"They should be more diligent about who they employ and have more safeguards to stop people slipping through the net."
The specialist aviation law team at Irwin Mitchell, which is representing British families, said it wanted to see "important lessons learned".
Irwin Mitchell say they hope it will feature recommendations to improve aviation safety including improved checks on the health of pilots and co-pilots, both physical and mental.
They want recommendations about guidance on access to the cockpit mid-flight.
The lawyers have also called for transparency and disclosure of medical records and details of the involvement of the US flight school where the co-pilot was trained.
Jim Morris, an expert aviation lawyer at Irwin Mitchell and former RAF pilot, who is one of the team representing the families involved, said: "The information about this tragedy has already been devastating for the families to hear."
He said they want to know why more was not done to prevent the co-pilot from flying "when it seems clear from the evidence already available that he was a potential risk to himself and passengers".
Morris added: "It's crucial that any reasonable recommendations made in the accident report to improve aviation safety are implemented as soon as possible.
"Nothing can turn back the clock or bring the innocent victims back but the families now want to see important lessons learned from this so that it reduces the risk of similar incidents.
"In particular the news regarding the extent of co-pilot Andreas Lubitz's medical history and the severity of his mental health condition raises very serious questions about how he was assessed and how the fitness of commercial airline pilots should be assessed."