Germanwings Flight 9525
The main hypothesis for the cause of the aircraft crash is that co-pilot Andreas Lubitz deliberately caused it to crash. The recording of one of the black boxes of the destroyed Airbus allows us to verify that Lubitz activated the closing of the cockpit door and deliberately began the descent of the plane over the mountains.  His breathing at the time of descent was normal and he ignored the captain's instructions to open the door, even when the latter tried to knock it down with an ax to regain control of the aircraft.