Abbreviation and Misinterpretation of 'Type c' Call Signs


To remind air traffic controllers and aircrews of the rules concerning the abbreviation of R/T call signs and to raise awareness of the potential for misinterpretation of some call sign alphanumeric flight identification suffixes that have a ‘leading zero’.


The EUROCONTROL Call Sign Management Cell (CSMC) has received a number of reports of call sign confusion caused by the incorrect abbreviation or misinterpretation of some “Type c” R/T call signs whose alphanumeric flight identification suffixes start with a zero.

ICAO Provisions

ICAO Annex 10, Vol II, Chapter 5, § states that there is no abbreviated form for “Type c” call signs (i.e. those that are formed by the R/T designator of the aircraft operating agency (e.g. ‘Highjet’), followed by the flight identification suffix (e.g. ‘123A’)).


In the occurrences that have been reported, the flight identification suffix of the call sign was alphanumeric and had a ‘leading zero’, e.g. Highjet 045K. These flight identifiers have sometimes been incorrectly abbreviated, e.g. Highjet 45K, or have been misspoken as Highjet 405K, which has contributed to some crews becoming confused about which flight is being addressed by ATC.

Your Attention Is Required

Air Traffic Controllers are reminded:

  • Not to abbreviate “Type c” call signs.
  • To be alert for the potential for misinterpretation of ‘leading zero’ flight identification suffixes, in particular those that involve alphanumeric characters.

Aircraft Operators are requested to note the subject and consider the relevance to their operational environment.

Further Reference


© European Organisation for Safety of Air Navigation (EUROCONTROL) August 2010. This alert is published by EUROCONTROL for information purposes. It may be copied in whole or in part, provided that EUROCONTROL is mentioned as the source and to the extent justified by the non-commercial use (not for sale). The information in this document may not be modified without prior written permission from EUROCONTROL. The use of the document is at the user’s sole risk and responsibility. EUROCONTROL expressly disclaim any and all warranties with respect to any content within the alert, express or implied.


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