November 10, 1972
Hijackers threaten to fly Southern Airways Flight 49 into a nuclear reactor. In response, the FAA requires airports to screen all passengers and their carry-on bags by January 5, 1973. The checkpoints will be overseen by the airlines and security personnel contracted from private companies.
August 5, 1974
Congress passes the Air Transportation Security Act, introducing and requiring metal detectors and X-ray screening of carry-on bags at ALL US airports. Consumer advocates sue, citing that the metal detectors are a violation of the Fourth Amendment's protections against unreasonable searches and seizures, and the courts agree. However, despite deeming them a violation, they also declare them legal so long as the screening is a) universal, and b) used only to search for weapons and explosives.