he didn't notice the plane go down in any way. it wasn't noticeable in terms of altitude changes. i guess my question to you is if someone's in there setting it from 100 feet to 49,000 feet back to 100 feet that doesn't register anywhere? with anybody? >> the plane was already in a cleared descent from about 39,000 feet to 21,000 feet. and so for him to spin the knob below the assigned altitude of 21,000 feet wouldn't change what the plane would do. if he'd gotten to 21,000 feet and hadn't changed it would have kept descending but there wouldn't be wild gyrations based on knob turns. because the plane was already in a descent. nobody would have noticed, including the captain. >> you feel everything's automated. what mary was saying there's no reporting back. there's no okay this guy tried to set to it 100 feet. if you saw someone try to do that you'd know you had a problem. >> well here's the thing that's kind of interesting.