Changing of Aircraft Call Sign

The authority to change the call sign of an aircraft resides with the air traffic controller in the interest of safety if there are two or more aircraft on the frequency with similar call signs. Here’s my experience and ICAO’s procedure on the subject.

On one occasion while on duty in the control tower, I changed the call sign of an aircraft because there was another aircraft on the same frequency with a similar call sign. Just when I though things were under control, all hell broke loose. I was challenged by the pilot-in-command who told me that I could not do that. I promptly responded saying that it was indeed my prerogative according to ICAO procedures. This of course was no consolation, but with much protest, the flight eventually got on the way.
The procedure to change the radio-telephony call sign of an aircraft is one that is not often used in my part of the world because of the relatively low traffic volume. I thought that the apprehension on the pilot’s behalf may have been from unaccustomed use.
Air traffic controllers, like many other professionals, have a vast array of procedures that can be employed when the right situation exists. As far as I am aware, no air traffic controller will attempt to apply a procedure that he/she cannot defend in a court of law. Apart from safety, liability is always at the forefront of a controllers mind.
Here’s what ICAO has to say on the matter, as outlined in Doc.4444 (PANS ATM) 15.7.5:

Change of radiotelephony call sign for aircraft
An ATC unit may instruct an aircraft to change its type of RTF call sign, in the interests of safety, when similarity between two or more aircraft RTF call signs are such that confusion is likely to occur.
Any such change to the type of call sign shall be temporary and shall be applicable only within the airspace(s) where the confusion is likely to occur.
To avoid confusion, the ATC unit should, if appropriate, identify the aircraft which will be instructed to change its call sign by referring to its position and/or level.
When an ATC unit changes the type of call sign of an aircraft, that unit shall ensure that the aircraft reverts to the call sign indicated by the flight plan when the aircraft is transferred to another ATC unit, except when the call sign change has been coordinated between the two ATC units concerned.
The appropriate ATC unit shall advise the aircraft concerned when it is to revert to the call sign indicated by the flight plan.

Here’s the applicable phraseology from Doc.4444:

So, for all those pilots who have yet to experience this unusual circumstance, please be guided accordingly.
Has anyone ever experienced a similar situation? I’d love to hear about it.

2 Responses

Jeff Kanarish

In 32 years of flying, in N. America, C. America, S. America, and the Caribbean, I have never had a call sign changed for my aircraft, nor have I ever heard it done to any other aircraft, even in the highest traffic density airports in the world. If there are similar call signs on the frequency, the controller will say, “Aircraft ABC, be advised Aircraft ABD, is also on this frequency,” or, “Attention, Aircraft ABC and Aircraft ABD, two aircraft with similar sounding call signs on this frequency.” Each pilot acknowledges and we move on.
This ICAO rule is so unused, I don’t think any pilot is aware of it. I think that’s why you got pushback from the pilot when you did it. It was not a challenge made on your character, ability, or knowledge of legalities. It was a defensive response to something extraordinarily different from what is generally expected.
On a side note, sorry I have not contacted you. The project I was working on got pushed to the back burner due to competing interests.

Wayne Farley

Hi Jeff, taking your experience into account, I see that this the procedure is rarely used in deed. I am surely happy to be bringing it to the attention of pilots so that they will not be apprehensive if they were to experience it for the first time.

About Wayne Farley

I am Wayne, a career air traffic controller with over 30 years of industry experience. Engage me while I share my thoughts, experience, and news from around the aviation world. A post titled “13 Characteristics of an Air Traffic Controller” written in 2010 went viral and established me as the unofficial ambassador of ATC.

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