The United States government created the Transportation Security Administration (TSA) in November 2001 through the Aviation and Transportation Security Act to centralize and professionalize the nation's security efforts following the September 11 attacks. Before the TSA, airport security was largely handled by private contractors hired by the airlines themselves, which led to inconsistent standards, poor training, and low wages for screeners. By "federalizing" security, the government aimed to create a uniform, high-standard screening process across all 450+ U.S. commercial airports. The TSA's mission was designed to expand beyond just airports to include the security of highways, railroads, ports, and pipelines. The creation of the agency also shifted the philosophy of travel security from "customer service" (focused on speed) to national security, introducing more rigorous passenger identity verification, the Federal Air Marshal program, and advanced technology for detecting explosives. In 2003, the TSA was moved from the Department of Transportation to the newly formed Department of Homeland Security.