This week a Germanwing's co-pilot Andreas Lubitz flew a jetliner into a French mountain. After further investigation, a letter was found in Lubitz's trashcan that said he was deemed unfit to work. Lubitz had kept this hidden from his employer. Investigators are still trying to figure out what was ailing Lubitz
See "Germanwings Co-pilot Andreas Lubitz Declared 'Unfit to Work,' Officials Say", Michael Pearson, CNN, March 26, 2015