Hello all,A few days ago while listening to Zurich tower on liveatc, I noticed that Lufthansa flights had different callsigns compared to their flight numbers. As far I know all major airlines use their names and flight numbers as callsigns (Turkish Airlines flight TK 1909 would be "Turkish 1909", same in US, usually name and flight number).Now, one Lufthansa flight that day was using the callsign "Lufthansa 6 Kilo Alpha". I assumed that those 2 letters were the last 2 of the aircraft's registration but of course I'm not sure of this.Does anyone know the reason? or is there a specific logic in assigning callsigns?Thanks in advanceOnurLTBA

It might have been a positioning flight where they didn't have a number already in the system. I've been on some positioning flights though and dispatch gave them a 'normal' type number with no other phonetics in it.

Onur,You're right, most flights have the airline callsign and the flight number but this is common practice not law. Technically the airline can use whatever callsign it likes.Some airlines will assign an alpha numeric callsign to a flight if they know there is another flight out there with a similar call sign (Lufty 162 and Lufty 172 for example). To help avoid any potential communication issues they could just call one of them Lufty 16K or something like that. Other airlines change the callsign on 4 digit flight numbers because Lufty 4691 can be a bit of a mouthful if you're saying it for a few hours (not that Lufty 16KA is any better but you get my point). Other airlines just make up callsigns as they see fit.To answer your question succinctly, there is little/no logic to callsigns, they are what they are.Hope this helps,Ian

Thanks for your replies gentlemen,Ian, I see your point, I suppose it's much harder to say LH 4691 than LH 6KA, it makes perfect sense since time is crucial for ATC while managing all those birds. Avoiding similar call signs as you stated is pretty obvious. The reason of my question was to put more reality in my simming.Again, thanks for your inputsHappy landings