Selective Calling (SELCAL) is an International Civil Aviation Organization (ICAO) managed communications method used to identify and then notify aircraft that a ground radio station wishes to communicate. A unique 4-character SELCAL code is assigned to each aircraft allowing airlines and communication providers to contact a specific aircraft on a common radio voice frequency. This means the aircrew can be alerted to a request for communications without having to listen continuously to messages for other aircraft. Despite the increasing capability of aircraft satellite communications, traditional long distance radio communications with SELCAL are still the backup systems for delivering Air Traffic Control (ATC) messages and other aviation communications to aircraft in remote areas of the world (and many aircraft still use these radio communications as their primary means of ATC communication over oceanic regions).
SELCAL codes began use in civil aviation in 1957 under the direction of ICAO. Shortly following SELCAL’s introduction, ICAO agreed to formally transfer the SELCAL registration and management functions to Aeronautical Radio Incorporated (ARINC). From that point, ARINC became the official registrar of all SELCAL codes, accepting all SELCAL applications directly, as well as providing an annual report to ICAO with a summary of SELCAL usage. In 2006, the ARINC section responsible for SELCAL was split of into a separate company called Aviation Spectrum Resources, Inc. (ASRI). Owned primarily by airspace users in Northern America, ASRI is now the official SELCAL Registrar for all SELCAL codes worldwide. The SELCAL register has now increased to 35,000 SELCAL code assignments and continues to grow with the demand for air travel.
Given the growth of SELCAL since its inception, there is a shortage of possible 4-letter codes. This has required re-use of the same code by more than one aircraft. Duplicate codes are usually assigned to aircraft operated in widely separated areas of the world, and usually do not have the same HF radio frequency assignment. However, there are occasions when two or more aircraft having the same code may be operating in the same general area, and will respond to the same transmission. Therefore, SELCAL should not be used as a substitute for proper voice identification procedures.
For more information, specific requests or to get answers to your questions, please submit a Service Request Form.