Even on a pure UI level, any software used in such a role really ought to warn the user somehow for "this aircraft has been X hours out of contact" in a world where this isn't supposed to happen anymore.
You also figure it out pretty quickly when you watch a few plans make physically impossible jumps between their dead reckoning location and their actual location.
You also figure it out pretty quickly when you watch a few plans make physically impossible jumps between their dead reckoning location and their actual location.