This document contains designators for aircraft operating agencies and for authorities and services associated with international aviation. The designators currently consist of:
a) three-letter designators intended for use on the international aeronautical telecommunications service;
b) telephony designators for aircraft operating agencies and for authorities and services operating aircraft, which may be used as appropriate.
In accordance with a decision of the ICAO Council, three-letter designators are being applied for all current purposes with effect from 25 October 1987. This document contains details of the three-letter designators which have been reserved for use by aircraft operating agencies, aeronautical authorities and services at the time of publication.
Three-letter designators may be used following the Location Indicator as the fifth, sixth and seventh letters of Addressee Indicators followed by the filler letter "X", or by a letter representing a department or division within the organization addressed, (see Annex 10 — Aeronautical Telecommunications, Volume II, 184.108.40.206.2) in the Shortened Address, Address, Origin and/or text parts of AFTN messages, (the filler letter need not be repeated in the text part of the message). The three-letter designator may also be used in the aircraft identification as used in the Flight Plan and associated messages (see Procedures for Air Navigation Services — Air Traffic Management (PANS-ATM, Doc 4444)).
For the convenience of message originators, the document also includes the postal and telecommunications addresses (commercial and aeronautical) of government civil aviation authorities.
Note.— The aeronautical telecommunications addresses in Part 4 include the appropriate three-letter designators and the filler letter "X", unless otherwise indicated.
Any additions, deletions, omissions or discrepancies should be communicated to the Secretary General, ICAO, 999 Robert-Bourassa Boulevard, Montréal, Quebec, Canada H3C 5H7.