entry if you know the code. but if the person inside the cockpit switches it to lock the keypad won t work for five minutes and there s another override that goes beyond five minutes. i can also override the keypad and hold it in the lock position and now he cannot use the keypad or enter the door while it is locked. reporter: no one can get in? no one can get in. reporter: to keep your co-pilot out, what do you do? if he knew the keypad number to get in i hold the lock and he cannot get in. reporter: can you manually fly this and hold the lock button? oh yes. easy. reporter: then that s a purposeful act? oh yes. reporter: again and again, we fly through the scenarios in autopilot and manual both managed to crash the plane and both had to be deliberately programmed or flown into the ground. what does that suggest to you as far as his determination?