The designators consist of: a) three-letter designators which are used primarily for messaging purposes on the international aeronautical telecommunication service and for aircraft identification by air traffic control (ATC); and b) telephony designators which form the prefix of the aircraft call sign and the call sign for aeronautical ground stations in radiotelephony communications . Parts 1, 2 and 3 consist of encode and decode tables linking aircraft operating agencies, aeronautical authorities and services with their assigned ICAO three-letter and telephony designators. Addresses of government civil aviation authorities are listed in Part 4.

Note.— Some parts of the document are given in English, Arabic, Chinese, French, Spanish and Russian. Other parts of the document are in English only.