I would call it a congressionally mandated "administrative" search that was reviewed by the Supreme Court.
I'm not saying I like it...I don't. But in today's world, it is a necessary evil or every whack job or religious zealot will try to make their statement at 36,000 ft.
The supreme court got it wrong. Look at the fourth amendment and tell me where the government has the right to stop and search me without probable cause. They're doing it probably cause.