Airlines may also check the mental health of pilots more. This is because the Germanwings co-pilot may have been depressed. He had a history of depression. His boss said he took several months off work and then had to retrain, but he was "100 per cent fit to fly". During the final moments of Flight 9525, he locked the pilot out of the cockpit. There was "absolute silence" in the cockpit as the co-pilot directed the plane into the mountain.