Doc 8585/147 Edition No. 147 / Édition n0147 / Edición num. 147 ...

3. Telephony designators
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3.1 Telephony designators for aircraft operating agencies may be used as part of the aircraft radiotelephony call sign
followed by the flight identification in radiotelephony communications» in accordance with the ICAO Radiotelephony Procedures
(Annex 10» Volume II» 5.2.1.7.2 refers). Example: "AEROFLOT 301".
3.2 In the registration of telephony designators the following rules will apply;
a) the telephony designator should resemble the name of the aircraft operating agency or its function and be distinct
and dissimilar from any other telephony designators in Doc 8585. Ideally it should reflect correlation between the
three-letter designator» the telephony designator and the name of the aircraft operating agency or its function
(examples: ARO - ARROW - Arrow Aviation; RAJ - RAJI - Raji Airlines);
b) in order to reduce the length of transmission the telephony designator should be brief» comprising if possible one
word of two or three syllables. It should not exceed two words;
c) three-letter designators may not be used in phonetic form as telephony designators. However» telephony designators
of long standing (such as KLM or TWA) may be retained» provided that an acceptable alphabetic representation is
used (example: KAY-ELL-EMM); and
d) the telephony designator should be easily and phonetically pronounceable in at least one of the following languages:
English» French» Russian» Spanish.
Note.— Resolution of similar sounding call-signs:
1) In the interests of safety, simple procedures should be developed by States and aircraft operating agencies for
detecting, reporting and eliminating those call signs which, because of their similarities to other call signs, may cause
confusion or mistakes in identification. When call sign similarity difficulties concern the telephony designator, the civil
aviation authority concerned should coordinate efforts to resolve the problem. This may require submission to ICAO
for a change in one or both of the conflicting telephony designators. Cooperation between civil aviation authorities is
required when the aircraft operating agencies are from different States.
2) In the selection of the flight identification number the following is recommended:
a) flight numbers should be kept as short as possible and usually be limited to three figures;
b) flight numbers should be selected bearing in mind the flight numbers already in use by other operating agencies
in the intended control environments; and
c) when practicable flight numbers other than those ending in a zero or five should be used.