Aircraft Callsign Question

ImDave

Hey guys,

I have a question which has I have never figured out or thought of asking over the last number of years about commercial aircraft callsigns. I have a quick listen sometimes to LiveATC when around the airport, and have noticed that many flights go by a different callsign to the actual flight number. For example at the airport this morning, EI202, which I would have assumed would simply be 'Shamrock 202' was referred to 'Shamrock 20 Alpha'. There was a Ryanair flight, FR1926, which was going under something like 'Ryanair 16 Bravo Juliet' or something similar.

Anyone care to enlighten me as I really can't figure it out! (It's not something to do with a combination of the flight number and tail reg is it?!)

irish atco

The short answer is that it is to cut down on Callsign confusion (whereby one aircraft may mistakingly take an instruction meant for another with a similar callsign). I dont have the stats, but Callsign confusion, in my experience, is a contributing factor in many incidents.
An airline may, for example, have flights numbered 202 212 222 232 etc, all departing around the same time. the use of letters is to assist in avoiding possible confusion.

im sure someone else may expand on the above