we don’t have jam-proof GPS??? Nonsense.
Methinks that dependency on advanced avionics, satellites, etc will not end well.
GPS relies on signals from satellites. Any device that relies on RF signals can be jammed. All the bad guy needs to know is the frequency band.
There are ways to mitigate rf jamming, but both the sender and receiver have to be on the “same page” so to speak. I don’t believe GPS satellites have that capability.