[fuzzmeister]

While there should certainly be a limit on the extent of searches at airports, the reason these searches have not been found "unreasonable" is likely that you can refuse to be searched. Sure, it means you're going to have to drive to wherever you're going, but you still have the option to refuse.

If, on the other hand, the police pulled you over and forced you to submit to some sort of full-body scan without reasonable suspicion, that would certainly be ruled in violation of the Fourth Amendment.