writes:

If the satellite system is jammed it's just not ONLY going to affect
small engine airplanes. I use the very same satellites in my Garmin
430 and 296 as the airliners do.

It will affect any aircraft dependent upon GPS, and without a VOR back-up,
that will be very dangerous. GPS is trivially easy to jam and almost as easy
to spoof. Airliners might get by en-route with INS, but small aircraft
dependent on GPS will be up the creek, and airliners on approach will be in
danger as well (especially if ILS is decommissioned, too). WAAS does not help.
LAAS is harder to interfere with but interfering with the LAAS transmissions
isn't absolutely necessary to mess up the system. RAIM doesn't help against
spoofing, and although it may detect jamming, that doesn't help much, either,
if you're entirely dependent on GPS and you no longer have it.

And in fact ADS-B is trivially easy to spoof, too. So the airplanes "seen"
via ADS-B may not actually be there, or they may not be where they appear to
be.