that the radios were shut down, possibly systematically. it would explain why there may not have been communication. >> are there any suspects? >> they've gone through everybody on the aircraft, and they've determined that there is no one there who would match the profile of someone who would take over that aircraft. >> if not human intervention, could something on the plane have malfunctioned? >> it's got to fly for another six hours. that's the problem with the mechanical questions. >> what kind of catastrophe could shut down the plane's communications but still have allowed it to fly? >> anybody that chooses to hang their hat on one scenario or the other, in my view, is heading for a fall. the entire experience of air crash investigations is that, yes, it's usually the obvious, but it's quite frequently something you've never even thought of.