mask if you were the pilots, and that the plane then goes on because this 777 is such a marvelous plane. the 777 will shut down systems if it's losing power, it will shut down systems and try to keep itself flying. it will keep its control surfaces and keep its engines. that's what makes the plane so great. >> professor, do you agree with what mary just said, or do you focus more on human intervention in this? >> well again, we have to keep all hypotheses open. it's hard to find a credible hypothesis where you have the sequence of events that we have here. if there was a problem on the airplane where you had let's say a cockpit fire or something like that, or depressurization, it could explain losing the transponder. it doesn't really make sense to head off in the direction the airplane headed off on. so they would have either done