In aviation, TSA stands for the Transportation Security Administration, a U.S. government agency created in response to the September 11, 2001, terrorist attacks. Operating under the Department of Homeland Security, the TSA's primary mission is to protect the nation's transportation systems, with its most visible role being the screening of passengers and luggage at more than 450 U.S. airports. Beyond the security checkpoints, the TSA manages the Federal Air Marshal Service, oversees the vetting of flight crews, and conducts risk assessments of airport perimeters. In 2026, the agency has moved toward "biometric-first" security, using facial recognition and CT scanners to speed up the process. While they are often associated with the "TSA PreCheck" program—which allows low-risk travelers to keep their shoes and jackets on—their authority actually extends to highways, railroads, and ports, making them the central regulatory body for all "intermodal" security within the United States.