The nationwide alert status has been raised from its current level of yellow (elevated) to orange (high) on five occasions. It has never been below yellow. New York City has remained at orange (high) since 9/11. In August 2006, the threat level for flights from the United Kingdom to the U.S. is raised to red, the first time that threat level has been used.
On April 26, 2011, the National Terrorism Advisory System (NTAS) replaces the color-coded Homeland Security Advisory System (HSAS). NTAS utilizes a vocabulary system including terms Elevated and Imminent.