On December 20, 2013, the Department of Homeland Security announced that implementation of Phase 1 would begin on January 20, 2014, which followed a yearlong period of "deferred enforcement". There are four planned phases, three of which apply to areas that affect relatively few people—e.g., DHS headquarters, nuclear power plants, and restricted and semi-restricted federal facilities such as military bases. On January 8, 2016, DHS issued an implementation schedule for Phase 4, stating that starting January 22, 2018, passengers with a driver's license issued by a state that is not compliant with the REAL ID Act (and has not been granted an extension) will need to show an alternative form of acceptable identification for domestic air travel to board their flight. Starting October 1, 2021 (originally scheduled for October 1, 2020 but was postponed a year due to a global coronavirus pandemic), every air traveler will need a REAL ID–compliant license or another acceptable form of identification (such as a U.S. passport, U.S. passport card, U.S. military card, or DHS trusted traveler card, e.g. Global Entry, NEXUS, SENTRI, FAST) for domestic air travel. , all states and territories have been certified as compliant except American Samoa and the Northern Mariana Islands, which are under review.