thegoaf,
Your wrong about making it so that it can't be jammed. Anything can be jammed. If man can make it, man can break it.
The US military GPS was supposed to be unjammable, but it is easily done because the people that designed it were to arrogant to know any better.
Even if the jammer is frequency chasing to catch up to the aircraft system it only has to dissrupt so many data packets to corrupt the commands enough that the plane won't know what to do.
