a.m. that's when the captain began knocking on the cockpit door. moments later, transponder data shows the autopilot was reset intentionally and by hand from 38,000 feet down to 100 feet. now, to help us understand how that situation could have transpired there on the plane, why the captain had no possible way of opening that door from the outside, we learn more about that from kyung lah. >> reporter: he cannot imagine why a pilot would do this. >> terrain, terrain. >> reporter: but bugs forsyth knows how. a retired military commercial pilot, forsyth says he's flown thousands of hours in the a-320 cockpit, one of the safest high-tech passenger jets used around the world. >> normal, lock, and unlock. >> reporter: he like all pilots has used the switch hundreds of