Listening Out Codes

Listening Out Codes

Best Practice – "Listening Out" Codes

Many GA aircraft do not like to use busy frequencies but they would like the re-assurance of knowing that ATC know where they are.

  • Provide a squawk to indicate that an aircraft outside controlled airspace is listening on the frequency. This enables a controller to contact that aircraft if it inadvertently strays into controlled airspace.
  • This ability is enhanced if Mode S radar and transponders are in use as the aircraft ID can be interrogated and the aircraft callsign established, even from a common squawk.

Cost – Some small publicity costs.


The UK has established a number of areas around infringement hotspots where “listening out” codes can be used. One of these is shown on the chart below and a full list is available at Controllers’ reports contain occasions when it has proven useful to call aircraft that have just infringed controlled airspace and give them navigational assistance before they have caused losses of separation.

Sample Material

Listening out code area around the Stansted CTR.

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