The Transportation Security Administration (TSA) is a U.S. agency under the Department of Homeland Security (DHS), created in response to the September 11 attacks to centralize and strengthen airport security. Congress authorized its formation through the Aviation and Transportation Security Act, signed by President George W. Bush on November 19, 2001; it initially operated under the Department of Transportation before moving to the DHS in March 2003, with headquarters in Springfield, Virginia. Although its official mission covers all transportation modes—including highways, railroads, and ports—its primary focus is preventing aircraft hijacking and screening passengers and baggage at over 450 U.S. airports. To accomplish this, the TSA employs more than 47,000 personnel, including Transportation Security Officers, bomb technicians, and Federal Air Marshals, operating on a fiscal year 2023 budget of roughly $9.70 billion. A notable historical detail is its massive 2002 hiring drive, which assessed 1.7 million applicants to fill 55,000 screening jobs—an effort comparable only to World War II military recruitment. Today, the agency uses identification checks, pat-downs, full-body scanners, and explosives detection, though it allows a few airports to use private screeners under its Screening Partnership Program (e.g., San Francisco and Kansas City); since its inception, it has faced criticism over procedural effectiveness, as well as controversies involving baggage theft, data security, and allegations of ethnic prejudice.