[AWildC182]

Just because there aren't $200 SDR transceivers available that can handle 20+GHz right now doesn't mean there won't be in the next few years. These protocols have to be designed with more foresight than simple availability barriers because the second you mass produce something, it and it's constituent parts are suddenly available.

That said, if you want to lose sleep at night, I suggest you look into the strict authentication and jamming resistance of ADS-B (effectively the aircraft equivalent of such a network).