I've seen different callsigns for en-route air traffic control, including Center, Radar, and Control (and Radio?). I suspect the only difference is the geographic location - Center in the U.S. (e.g. Salt Lake Center) and Radar and Control in Europe (e.g. Langen Radar, London Control).

Are there any other differences besides location? (is the location-assumption correct?) If not, why is it not standardized then?


The 'Center' suffix is indeed more common in the US for the en-route call-signs under radar control. There is also New York Radio, for example, for the non-radar service over the Atlantic. Another example is the 'Director' suffix that is not common in the US, but is common elsewhere for the final approach controller.

In this case we need a referee, enter ICAO Annex 10 Volume II Communication Procedures: The unit or service shall be identified in accordance with the table below except that the name of the location or the unit/service may be omitted provided satisfactory communication has been established.

Unit/service available                Call sign suffix

area control centre                   CONTROL
approach control                      APPROACH
approach control radar arrivals       ARRIVAL
approach control radar departures     DEPARTURE
aerodrome control                     TOWER
surface movement control              GROUND
radar (in general)                    RADAR
precision approach radar              PRECISION
direction-finding station             HOMER
flight information service            INFORMATION
clearance delivery                    DELIVERY
apron control                         APRON
company dispatch                      DISPATCH
aeronautical station                  RADIO

Above are the standards, but nations are free to deviate. Below is from the UK AIP listing the differences:

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And from the US AIP:

Facility                                         Call Sign

Airport UNICOM                                   Shannon UNICOM
FAA Flight Service Station                       Chicago Radio
Airport Traffic Control Tower                    Augusta Tower
Clearance Delivery Position (IFR)                Dallas Clearance Delivery
Ground Control Position in Tower                 Miami Ground
Radar or Nonradar Approach Control Position      Oklahoma City Approach
Radar Departure Control Position                 St. Louis Departure
FAA Air Route Traffic Control Center             Washington Center

The U.S. does not use the term "area control service" to indicate controlled flight in controlled areas. The U.S. equivalent facility for an Area Control Centre (ACC) is an Air Route Traffic Control Center (ARTCC).

Related: Where to find the callsigns of the en route controllers?


Actually, it is standardized, but not in the way you assume.

The suffix ("radio", "information", "radar", etc.) specifies the type of services offered by the station or, in some cases ("ground", "approach", etc.), the type of traffic or phase of flight handled by the station.

For example, a station named Springfield Radio won't offer radar or ATIS service; if it did, the suffix would be different ("Radar" and "Info", respectively, in this case). Just by a quick glance at the call sign, or overhearing it on the radio, the pilot can know what to expect from them.

Consequently, if Approach hands the aircraft off to Control during approach and landing, the pilot knows that something is probably amiss and can ask for confirmation; but if Approach hands them off to Tower or Tower hands them off to Ground, they know that all is probably well.


There are a number of different "ATC" authorities:

Ground Control☆

Responsible for the movement areas on the physical airport. This includes both aircraft and airport service vehicles. Aircraft refer to this as "Ground".

Clearance Delivery☆

Gives an aircraft IFR (or sometimes VFR) clearance for flight plans.


Manages arriving and departing aircraft, usually takes over responsibility for aircraft as they approach a runway (take-off clearance) or as they approach the airport (hand-over from approach control).

Departure Control☆

Manages the airspace around the airport for departing flights providing separation and routing. Sometimes combined with Approach Control.

Approach Control☆

This is the first authority you talk to that is actually located at the airport. Manages spacing and arrivals and usually assigns runways. Also called "Terminal Control" and may be combined with departure control.


This is the authority you talk to when you are going between airports. Usually a center controls a large area of airspace and can manage aircraft in those areas. Here are a list of FAA Centers, called "Air Route Traffic Control" or ARTCC for short. On the radio pilots usually use the term "Center".

Flight Service Station

This is a service provided to pilots but is not an air traffic control authority. Pilots may open/close flight plans or get en-route weather information on these frequencies. They are usually called "Radio", for example, "Stevens Point Radio, N12345 on 131.2"...

☆ - Typically located on the airport which the pilot is operating. This is not always the case though, there are remote towers and satellite airports that may include these services but not have them co-located with the field.


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