In the United States, the Homeland Security Advisory System (HSAS) was a color-coded terrorism threat advisory scale created in March 2002 under the Bush Administration in response to the September 11 attacks. The different levels triggered specific actions by federal agencies and state and local governments, and they affected the level of security at some airports and other public facilities. It was often called the "terror alert level" by the U.S. media. The system was replaced on April 27, 2011, with a new system called the National Terrorism Advisory System.
