a suggestion that the acars system had been shut off before the last voice transmission. i learned that doesn't appear to be the case, all right, good night, a vocal good-bye before the system started being disabled or shut off. what does that tell you? >> that says that everything at that point seems fine. if only one was involved in some sort of a plot, the other could give a signal. verbal signals, transponder signals. you would think someone would have said something. the co-pilot does do the transmissions and to handle the radio. it turn off a cars, the aircraft communications and reporting system, you have to pull the fuse or cut the circuit breaker. it is not like you can just switch it off and then the screen would turn dark. >> failing that, if it had been a catastrophic failure, mechanical failure, we've talked