LOCATION INDICATORS INDICATEURS D'EMPLACEMENT ...

2.5 Other assignments
2.5.1 In exceptional cases, geographical locations other than those served by the AFS may be given a location indicator at
the discretion of the State having jurisdiction over the location concerned.
2.5.2 States that have introduced the predetermined distribution system 1 for AFTN or AMHS messages may assign for that
purpose location indicators constituted as follows:
First and second letters — the first two letters of the location indicator for the AFTN/AMHS communication centre
designated as the international terminal centre for the receiving State.
Third and fourth letters — the letters “ZZ” indicating a requirement for special distribution.
3. CHANGES IN THE ASSIGNMENT OF LOCATION INDICATORS
3.1 Location indicators once assigned should only be amended after paying due regard to the worldwide repercussions of
such changes upon all users of the communication services.
3.2 A location indicator should not be reassigned to another location for a period of at least six months after cancellation of
its previous assignment.
3.3 Changes in the assignment of location indicators should be promulgated by NOTAM or AIP as far in advance of the
effective date as practicable.
4. USE OF LOCATION INDICATORS
4.1 Location indicators that are assigned to locations to which messages cannot be addressed over the AFTN should be
identified by an asterisk (*).
E 0-7
4.2 A location indicator alone does not constitute an addressee indicator or an originator indicator in AFTN messages. The
aeronautical authority, service, unit or aircraft operating agency originating the message, or to whom the message is addressed,
should be identified by adding to the location indicator the appropriate ICAO three-letter designator, as listed in Doc 8585 —
Designators for Aircraft Operating Agencies, Aeronautical Authorities and Services.
4.3 Identification of radio transmission
ICAO location indicators should not be used for the identification of radio transmissions in lieu of “call signs” which are
prescribed for this purpose in Article 19 of the ITU Radio Regulations (Geneva, 1959).
5. ADDRESSES OF CENTRES IN CHARGE OF FIR/UIR
5.1 For the purpose of addressing ATS messages to ATS centres (FIC/ACC) in charge of FIR and/or UIR, a system of
addressee indicators has been devised.
5.2 Such an addressee indicator consists of the location of the ATS centre in charge, plus one of the following four-letter
designators:
ZQZX if the message is related to an IFR flight, or
ZFZX if the message is related to a VFR flight.
5.3 To assist in the correct addressing of the above-mentioned ATS messages, this section contains a list of FIR/UIR with
the centres in charge of those regions and their respective location indicators.
__________________
1. For details, see Chapter 4 of Volume II of Annex 10 — Aeronautical Telecommunications and Appendix 5 of Annex 15 — Aeronautical
Information Services.