so you know, once you've set the new flight level and you hit your flight level change button, you've turned your heading around, the aircraft will descend under automatics, even if the pilots then become subsequently unconscious. that's not particularly surprising, if that was the case. but did they descend 12,000 feet? we don't know. and if they did, it would have been a rapid descent. >> here's what's so confounding about all this, 15 days, and we get each of these puzzle pieces, they don't seem to fit together, and we're not even quite sure exactly how this all comes into one picture of what happened to this plane. could it be that something happened here that we have never seen before? i mean, these flights, these planes, this piece of machinery is so high tech, built with so many redundancies. are we using our past experience to try to explain a mystery that might be something completely new that we just can't describe yet? >> well, it's possible, but it does conform to two or three