Selective Calling (SELCAL)

Selective Calling (SELCAL) is an International Civil Aviation Organization (ICAO) managed communications method used to notify aircraft that a ground radio station wishes to communicate.  SELCAL works by each aircraft being assigned a different 4-character SELCAL code that allows airlines and communication providers to contact a specific aircraft on a common radio voice frequency.  This means aircrew are 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 radio communications with SELCAL remain in extensive use for delivering Air Traffic Control (ATC) messages and other aviation communications to aircraft in remote areas.

For more information, please see How SELCAL Works

For SELCAL applications, please use the Online SELCAL Application

SELCAL History

SELCAL began use in civil aviation in 1957 under the direction of ICAO.  Shortly after the introduction of SELCAL Operations, ICAO formally transferred the SELCAL registration and management functions to Aeronautical Radio Incorporated (ARINC).  From that point, ARINC became the official registrar of 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 re-structured into a separate company called Aviation Spectrum Resources, Inc. (ASRI).  ASRI is now the official ICAO SELCAL Registrar for all SELCAL codes worldwide.

Given the growth in the demand for SELCAL codes, there is a shortage of available 4-letter codes.  This shortage has required re-use of the same code by more than one aircraft. The number of SELCAL codes registered has now increased to 35,000 SELCAL code assignments, over three times the number of available unique SELCAL code combinations.

Where possible duplicate codes are 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 multiple aircraft having the same SELCAL code may be operating in the same control area, and may respond to the same SELCAL transmission. Therefore, SELCAL should not be used as a substitute for proper voice identification procedures.