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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, the ICAO 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.
Its headquarters are in Montreal, Canada.
The ICAO should not be confused with the International Air Transport Association (IATA), a trade organization for airlines also headquartered in Montreal.
Both ICAO and IATA have their own airport and airline code systems. ICAO uses 4-letter airport codes, and 3-letter airline codes.