function shortly after the last communication. it could have experienced an electrical problem. the component could have failed or it could have been switched off. we don't know. but what we do know is that the data link system known as acars was stopped from transmitting data, but the unit itself continued to talk to the satellites. that takes specialized knowledge and it takes some deliberate key strokes into the computer system to disable its ability to transmit data. that's a deliberate act by someone with knowledge. and so that is an important distinction and difference between all the other forms of the communication. >> right. >> and the acars system. >> but chris -- >> still with the position that it was a catastrophic moment? it seems that that would require a loft coincidences for that to be the case. >> this -- we have a lot of holes in every scenario that we've looked at.