Aviation security since 9/11

The 9/11 attacks had a global impact and triggered a two-wave response to improving aviation security. The first wave was characterized by the immediate response of the United States, which began exploring measures to further enhance aviation security. This response and subsequent responses have affected physical and watch-list elements of passenger screening and the carry-on, checked, and cargo elements of baggage screening. The subsequent responses constitute the second wave, characterized by the changing risks and threats posed to U.S. aviation security