A location identifier is a symbolic representation for the name and the location of an airport, navigation aid, or weather station, and is used for manned air traffic control facilities in air traffic control, telecommunications, computer programming, weather reports, and related services.
The International Civil Aviation Organization establishes sets of 4-letter location indicators which are published in ICAO Publication 7910. These are used by air traffic control agencies to identify airports and by weather agencies to produce METAR weather reports. The first letter indicates the region; for example, K for the contiguous United States, C for Canada, E for northern Europe, R for the Asian Far East, and Y for Australia. Examples of ICAO location indicators are RPLL for Manila Ninoy Aquino Airport and KCEF for Westover Joint Air Reserve Base.