The co-pilot who deliberately crashed a plane in the French Alps March 24 with the loss of 150 lives had a history of depression, it has been reported. The focus on Andreas Lubitz’s mental health comes after a French prosecutor concluded the 27-year-old had deliberately flown the Germanwings Airbus 320 into the mountainside, killing all those on board. According to reports in German newspaper Der Spiegel, police searching Lubitz’s apartment in Dusseldorf have found evidence that he was mentally ill, although the nature of the evidence has not been disclosed. Meanwhile, German prosecutors have said there are indications the co-pilot concealed his illness from his employer, hiding a sick note for the day of the crash. Matthias Gebauer, chief correspondent for the online edition of Der Spiegel, tweeted that “Schoolmates of co-pilot who crashed tell German reporters he took six-months break from flight training in 2009 due to burnout syndrome.” The head of Lufthansa, the budget airline’s parent company, has already admitted Lubitz had taken the lengthy break from training. While chief executive Carsten Spohr did not give a reason for this interruption, German media reported he was suffering from “burnout or depression.” Spohr said, “I cannot tell you anything about the reasons of this interruption, but anybody who interrupts the training has to do a lot of tests so the competence and fitness would be checked again.” According to Lufthansa, Germanwings pilots undergo medical tests once a year. However, they are only required to undergo psychological tests once, before they are accepted as pilots. Lubitz also underwent a regular security check on Jan 27, and nothing untoward was found, the local government in Dusseldorf said. Previous security checks in 2008 and 2010 also revealed no problems. Lubitz had been employed as a flight attendant before training to be a pilot at the Lufthansa flight school in Bremen. He also underwent training in Phoenix, Arizona. Lubitz joined Germanwings in 2013 and had clocked up 630 flying hours before the disaster.