A quick LEXIS search shows:
Chandler v. Miller, 520 U.S. 305, 323, 137 L. Ed. 2d 513, 117 S. Ct. 1295 (1997) ("Where the risk to public safety is substantial and real, blanket suspicionless searches calibrated to the risk may rank as 'reasonable'--for example, searches now routine at airports and at entrances to courts and other official buildings."); see also United States v. Edwards, 498 F.2d 496, 500 (2d Cir. 1974) ("When the risk is the jeopardy to hundreds of human lives and millions of dollars of property inherent in the pirating or blowing up of a large airplane, the danger alone meets the test of reasonableness, so long as the search is conducted in good faith for the purpose of preventing hijacking or like damage and with reasonable scope and the passenger has been given advance notice of his liability to such a search so that he can avoid it by choosing not to travel by air.") (quoting United States v. Bell, 464 F.2d 667, 675 (2d Cir. 1972) (Friendly, C.J., concurring)).
See also United States v. Kincade, 379 F.3d 813, 822 (9th Cir., 2004)--Even the 9th has no prob with these types of searches.