different how you shut them down. >> martin, and maybe this is more of a question for your pilot there, mitchell, but why is it possible -- because i've gotten this question a lot from viewers. why is it possible to even shut down the transponder. why can pilots have that ability? >> the only reason that we have an off switch, anderson, is when we're on the ground. after you're on the ground and land and taxi off the runway, you're no longer a factor for any traffic so there's no point in you being on the screen, you turn it off and save the air traffic controllers the hassle of trying to declutter the screen. >> but never in the air, only once on the ground and the flight is over. >> richard, the fact that the acars was not functioning, again, we don't know why, what does that tell you? >> what it tells me is that either it was disabled and degraded or something so dramatic happened that it -- that it literally cut it off. but here's the problem with that