Headquartered in Montreal, Canada, the International Civil Aviation Organization (ICAO), an agency of the United Nations, develops the principles and techniques of international air navigation and fosters the planning and development of international air transport to ensure safe and orderly growth. The ICAO Council adopts standards and recommended practices concerning air navigation, prevention of unlawful interference, and facilitation of border-crossing procedures for international civil aviation. In addition, it defines the protocols for air accident investigation followed by transport safety authorities in countries signatory to the Chicago Convention. See NTSB, TSB, AAIB, BFU, and BEA.
Both ICAO and IATA have their own airport code systems. See ICAO airport code.