this is going to be through a pretty extensive face-to-face interview with the valuee. i'm going to review all mental health records current and past. >> reporter: even if a pilot is suffering from a disorder like depression or anxiety, it's up to them to seek help or their colleagues to report it. >> when an individual doesn't self-report, and if there aren't any overt signs amongst co-workers or airline personnel, if there's no legal involvement, it's pretty difficult to be able to identify the presence of a condition. >> reporter: deliberate crashes of commercial airplanes are extremely rare. but when underlying conditions and emotions enter the cockpit, there can be devastating cons consequences. in 1999 an egypt air copilot downed the 767 carrying 217 into the atlantic ocean, saying "i rely on god" as he steered the plane down. and in 2013 a mozambique airlines pilot locked the copilot out of the cockpit before crashing the plane to the ground. and now this. as investigators are still putting the pieces together. so far, there are no signs of a suicide note or any