Are callsigns AOC specific?

[ManaAdaSystem]

Just wondering why, for instance, Easyjet use three different callsigns, Easy, Topswiss and Alpine? I know they are different companies, but still owned by Easyjet. Are there rules that stop them from using "Easy" for alle three airlines?

[TCAS FAN]

Originally Posted by ManaAdaSystem

Just wondering why, for instance, Easyjet use three different callsigns, Easy, Topswiss and Alpine? I know they are different companies, but still owned by Easyjet. Are there rules that stop them from using "Easy" for alle three airlines?

They are specific to individual AOCs. All used internationally have to be registered with ICAO who allocate a radio call sign together with a three letter “operating agency designator” for flight plan use. The allocations are.listed in ICAO Document 8585 “Designators for Aircraft Operating Agencies”.

Only EasyJet UK can use “Easy” and the three letter designator EZY.