Aeronautical station (and therefore, ATS unit) callsigns normally comprise two parts: the name of a location and a suffix. ICAO Annex 11 recommends that the first part (the location name) is:
- for an Area control centre (ACC) or a Flight information centre (FIC) - a nearby town/city or a geographic feature
- for an Aerodrome control tower or an Approach control unit - the name of the aerodrome served
The suffix indicates the type of service being provided (the examples below are defined in ICAO Doc 9432):
- CONTROL (area control centre)
- APPROACH (approach control)
- ARRIVAL (approach control radar arrivals)
- DEPARTURE (approach control radar departures)
- RADAR (a general designation of a station providing radar service)
- TOWER (aerodrome control)
- GROUND (surface movement control)
- DELIVERY (clearance delivery)
- PRECISION (precision approach radar)
- HOMER (direction-finding station)
- INFORMATION (flight information service)
- RADIO (a general term for an aeronautical station)
Examples of ATS unit callsigns:
- Frankfurt (location) Tower (service)
- Barcelona Control
- Brussels Arrival
- Luxembourg Delivery
- Wien Ground
- Sofia Approach
When satisfactory communication has been established, and provided that it will not be confusing, the name of the location or the callsign suffix may be omitted.
The name of the ATS unit (the first part of the callsign) is normally used to identify the corresponding volume of airspace where the unit provides service (e.g. an FIR, control zone or control area). This is an ICAO recommendation. For example, the ATS unit Marseille Control provides service in Marseille FIR. Sometimes, however, an ATS unit provides service in more than one airspace. For example, Ankara Control serves both Ankara FIR and Istanbul FIR. It is also possible that more than one ATS unit provides service in an FIR. For example, area control service in the Athinai FIR (Greece) is provided by Makedonia Control and by Athinai Control.
The name of a rig/platform/vessel is normally used as a callsign by offshore mineral extraction agencies, i.e. the radio callsign is identical to the markings on the landing site. This is done in order to avoid confusion and prevent landing on the wrong platform.
In some countries other suffixes are used in addition to or instead of the ones provided above. Examples of these are DIRECTOR (a type of approach control service that provides vectoring to inbound aircraft) and TALKDOWN (instead of PRECISION) that are used in the UK.
Other suffixes may be used to indicate the type of the ground station that is not an ATS unit, e.g. DISPATCH for a company dispatch.
- ICAO Annex 10: Aeronautical Telecommunications
- ICAO Annex 11: Air Traffic Services
- ICAO Doc 4444: PANS-ATM
- ICAO Doc 9432: Manual of Radiotelephony
- CAP 413: Radiotelephony, UK CAA, 23rd edition, effective 17 August 2020