While this was happening, the United States government changed in a few ways. The United States Department of Transportation (DOT) created the Transportation Security Administration (TSA). Before 9/11, security at American airports was provided by the airlines. The TSA made it the government's job to provide airport security. New officers were hired by TSA to work at airports and to fly on planes as air marshals. The TSA also provides security on American trains and subways. A new Department of Homeland Security was also created. It became their job to protect Americans and their property inside the United States. When this department was created, the TSA moved from the DOT to Homeland Security.