high-tech passenger jets used around the world. >> normal, lock, and unlock. >> reporter: he like all pilots has used the switch hundreds of times. >> the unlock you have to pull up and hold it. a light comes on, says the door's open. but if i release it it goes back to normal position. >> reporter: norm means that it's locked. >> norm is locked. that's correct. >> reporter: according to an airbus operations video, there's a keypad entry on the outside that allows 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 locked position, and now he cannot use the keypad or enter the door at all. it is locked. >> reporter: no one can get in? >> no one can get in. >> reporter: so to keep your co-pilot out what do you have to do? >> to keep him out if he knew the keypad number to get in i just hold the lock. he cannot get in. >> reporter: can you manually fly this and hold the lock