ICAO has assigned air operator designators since 1952 to users through their State of the Operator. 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.

The designators support the SARPs of Annex 10, Vol. II, para. and ICAO’s designator assignments and are intended to be a reflection of States’ lists. Three-letter designators serve three main operational purposes:

  1. Aircraft identification for Air Traffic Control (safety);
  2. Recognition of the operator for issuance of over flight and landing permissions and obtaining airport landing slots (safety and efficiency);
  3. Addressing of messages on the AFN (safety and administrative).


ICAO is offering an online database application that will offer benefits for States in the form of faster turnaround time for approving and confirming new assignments, and providing real-time data for ATS use. At the same time, ANB will work with States to eliminate unneeded and obsolete designator assignments, which will enhance safety by allowing better choice of designators for new assignments and more efficient use of the data overall.

The online data will provide a benefit for the operator, by permitting States and ATS authorities to easily verify the validity of the operator’s designator assignment. This is currently an administrative function required of the operator when applying for flight permissions. This can be promoted as an added value for the operator.

ICAO’s role:

  • Manages the assignment of designators to ensure consistent international usage in conformity with current SARPs and communications technologies.
  • Publishes current designator assignments in Doc 8585 (issued quarterly).
  • Receives requests for designators from the State having jurisdiction over the operator by mail, fax or e-mail.

The State’s role:

  • To validate operator’s need for ICAO designators and to submit the request to ICAO.
  • To liaise between ICAO and the air operator during the assignment process.
  • To notify the operator of ICAO’s issuance of their requested designators.
  • To notify new designator assignments to all concerned ATS authorities through Doc 8585.