Germanwings crash opens debate over medical privacy after Andreas Lubitz concealed his mental illness

Alone in the cockpit in control of Germanwings Flight 9525, Andreas Lubitz was harbouring a deadly secret.

Ignoring instructions from his doctor, who certified him unfit to fly on the day the plane crashed into the French Alps, the 27-year-old appears to have single-mindedly set in motion the chain of events that resulted in the worst air disaster for the low-cost airline and its parent Lufthansa, killing all 150 people on board.

Strict medical privacy laws mean the companies were oblivious to the potential dangers lurking in Lubitz's mind as the first officer took the plane into a steep descent over the region that members of his local gliding club, where he developed his passion for flying, had toured in the past.

Confidentiality regulations, designed to protect medical data and encourage people to consult doctors without fear of repercussion, put the onus on patients to disclose potentially hazardous diagnoses to authorities and their employers.

"The medical secrecy rules are centuries old and touch the core of the medical profession," said René Steinhaeuser, an attorney at Wigge lawyers in Hamburg who specialises in medical law. "Without that, the relationship between physician and patient, and thus the medical system as a whole, wouldn't work."

The case is sparking debate over how practices may be changed as a result of the tragedy. It also raises questions about Lubitz's period of absence from flying school that delayed his qualification to fly.