Requests for the registration of, or modification of a three-letter or telephony designator will only be recognized by ICAO when received from the State having jurisdiction over the aircraft operating agency, aeronautical authority or service concerned. Such requests should be made through the 3LD System at http://www.icao.int/3ld. Detailed processing instructions on how to use the system are contained in the online webpage.
The same designator will not be registered for more than one aircraft operating agency, aeronautical authority or service.
No more than one three-letter or telephony designator will be registered for each aircraft operating agency, aeronautical authority or service.
When a designator is no longer required, ICAO should be informed immediately. Any such designator so released will not be reassigned until a period of at least 60 days has elapsed.
Each Contracting State should review, at least annually, all of the designators and associated information in Doc 8585 for which it is responsible and advise ICAO of any other changes which should be made to this document in order to bring it up to date, such changes will be made through the 3LD System.
The rules governing the registration or change of three-letter and telephony designators are as follows