> I'd be kinda shocked if airplanes were just jam-syncing the clocks of their nav computers to the output of a GPS, and then had those nav systems be dependent

> I'd be kinda shocked if airplanes were just jam-syncing the clocks of their nav computers to the output of a GPS, and then had those nav systems be dependent on that time Obligatory not an aircraft software engineer, but I can say with some certainty that this is not the case. Aviation software, despite the recent issues with the 737 MAX, is generally designed and implemented to very high level of redundancy and SPOF-avoidance. From an airbus manual, to give you some idea: A300-600s, A310s, A320s, A330s and A340s with GPS PRIMARY The navigation system of these aircraft consists of 2 FMS, 3 IRS, 2 GPS and radio navaid sensors. The GPS position is primarily used for FM position updates, however if GPS PRIMARY is lost, FM reverts to radio updates or to IRS ONLY navigation when outside radio navaid coverage. FM(S) = Flight Management (System). IRS = inertial reference system (THREE of them). If GPS is lost or malfunctioning, the FMS falls back to that - which is periodically updated by reference to RNAV ground-based radio beacons. GPS could simply switch off worldwide and aircraft would be fine, just like they were pre-GPS. There is no conceivable reason the navigation system would especially care about the time being received from its GPS units, let alone perform some critical calculation based upon it. This article is pretty uninformed fear-mongering.