at this point in the investigation, there is no evidence one way or the other. >> but there would be piles of evidence if acars hadn't stopped transmitting. >> you would know the air-condition of the engines, the route it was taking, tatthe altitudes it was taking. we would know exactly the state of that aircraft. >> just the kind of information someone taking over a plane wouldn't want anyone to know. >> if you were doing something nefarious, then switching off acars would be a crucial part of making the plane go dark. >> 17 minutes after the plane went dark, 19 minutes after the last words from the cockpit, there was still no check-in with vietnam air traffic control. a call former chief pilot nick