As an American citizen, without reasonable suspicion of criminal intent, why are searches of this type legal? Has this been challenged in the Supreme Court?
We have held that airport screening searches, like the one at issue here, are constitutionally reasonable administrative searches because they are “conducted as part of a general regulatory scheme in furtherance of an administrative purpose, namely, to prevent the carrying of weapons or explosives aboard aircraft, and thereby to prevent hijackings.” United States v. Davis, 482 F.2d 893, 908 (9th Cir.1973); see also United States v. Hartwell, 436 F.3d 174, 178 (3d Cir.), cert. denied, 549 U.S. 945, 127 S.Ct. 111, 166 L.Ed.2d 255 (2006); Marquez, 410 F.3d at 616.
The unanimous opinion of the 9th (en banc); extremely unlikely to be overturned. Net-net: you concede the reasonableness of TSA searches by opting to get on a commercial airliner, where your personal safety impacts the safety of hundreds of other people. There are plenty of other ways to effect interstate travel without entering into the same risk equation; they're just less convenient.
It's kind of like saying walking on a wood-bottomed rope bridge is the same as walking on a suspension bridge. Except the rope bridge is a couple miles in the air. Essentially perfectly safe, but if one person cuts the ropes, you all go down. If someone decides to take out a chunk of a road's bridge, there's more danger to the people nearby than to the bridge as a whole; it's much closer to the same risk you run by simply standing near someone else.
Then, there's always those pesky squirrels deciding the rope looks tasty (ie, geese + engine). That's a different problem entirely, though.
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.