Also, if these foreign aircraft contained "precious cargo" or were part of anything deemed classified, would they really be on a system any random asshole could monitor? I would imagine IFF transponders would be disabled and the US military would be running things. Like an aircraft without an IFF signal pops up on radar, ATC attemp  5aa2  ts to hail it, and then gets a response from an F-class escort telling them shit's military and it's cool... or something.