software malfunctions in the past? could this have sent the plane to stall and plummet on this flight? bill? >> i'm unclear about your question. but the airplane is very stable aircraft. and very easily controllable by experienced and trained pilots. so they just don't fall out of the sky. >> they just don't fall out of the sky. have something here we have to get to before the top of the hour. someone says, a pilot, the same pilot says, i say good night all the time, and i say good morning. he said, if the ttcas was turned off you wouldn't know if an airplane was near you. commercial planes do not have radar that picks up airplanes. the only radar is for weather detection and tcas traffic collision avoidance system. i said, can a plane shadow another at that altitude? he says the military does it all the time for refueling. >> yes, under the most perfect conditions. you're talking about two civilian aircraft shadowing each