not just the airplane but electronics in general. you'd almost have to be electronics engineer to disable acars. you could reduce functions, simplify functions, get it back to raw data. you couldn't completely shut it down unless you had -- almost to the point of knowing how it's designed. >> that's why investigators don't know whether somebody had the sophistication and disabled it or something else was going on in the plane that took out the system. fair assumption? >> yes, that's a fair assumption. the latter seems a lot less likely. it's so sophisticated, so many backups. it's designed to not go out. i bet on somebody knowing how to disable it. >> we're well on our way on a whole different course. >> martin, mitchell, thank you very much. appreciate the time you're spending up there. it's helpful for people to put