25 years after 9/11, air travel security remains transformed

Twenty-five years after the September 11, 2001, terrorist attacks, air travel security has been fundamentally reshaped. The attacks, carried out by Al Qaeda hijackers, led to a paradigm shift in aviation security, moving from a system of private screening companies to a federalized approach.

The Aviation and Transportation Security Act, enacted in November 2001, established the Transportation Security Administration (TSA). By November 2002, TSA employees had replaced private screeners at airport checkpoints nationwide. This federalization introduced new norms for air travel, including stricter baggage screening, body scanning, and limitations on items like water bottles. Some US airports continue to utilize private contractors under the TSA's Screening Partnership Program, a model that the Trump administration sought to expand.

Beyond passenger screening, aircraft security was significantly enhanced. Cockpit doors were reinforced to be bullet-resistant and equipped with stricter access protocols, preventing flight attendants from opening them from the outside once locked. The number of federal air marshals on flights also increased.

Arik Arad, who has advised on aviation security and previously served as head of security at Israel's Ben Gurion Airport, described the post-9/11 security philosophy as a layered approach. "The principle is simple — if one layer fails, another should detect or stop the threat," Arad told Business Insider. He emphasized that intelligence, passenger assessment, screening, baggage security, airport access control, aircraft protection, trained personnel, and law enforcement became an interconnected system, a change in philosophy he deemed more important than any single technology introduced.