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. 18.104.22.168.2 and 22.214.171.124.2. ICAO’s designator assignments and are intended to be a reflection of States’ lists. Three-letter designators serve three main operational purposes:
- Aircraft identification for Air Traffic Control (safety);
- Recognition of the operator for issuance of over flight and landing permissions and obtaining airport landing slots (safety and efficiency);
- Addressing of messages on the AFN (safety and administrative).