flt # vs Flt. identifier

[Ari707]

Just wondering why some airlines (British, Virgin, Swiss, United, Alitalia) us flight identifiers ie: 23Y, vs the actual flight number for atc?

[moose135]

Among other reasons, they may have similarly numbered (or similarly sounding) flights in the same region at the same time, and it helps avoid confusion.

[hiss srq]

Apparently at least in the UK for some reason this is becoming very common place I have noticed as far as the letter attachment to the end of a flight number/callsign.... Here in the USA it is common place that we will use such "tags" on flights that are not nonstop... For example... Many times the last couple of CLT to LGA flights of the night will have this done because the SFO-LGA segment might still be in flight when the CLT-LGA flight departs CLT..... Hope that clears it up for you a little bit.

[Speedbird1]

I was wondering the same thing. For instance, Alitalia flight 608 is always identified as AZA 60U.