We could also model it after Star Wars, where we give the squadron a name and append a number to it to create a unique callsign (eg. Red 1 is the leader of Red Squadron)
Alternatively, if you’re worried about appropriateness, you could just name the squadron after the mothership. Raven 1 would be the leader of the squadron on Raven, for instance, or even just R1 for simplicity.
Once that fighter is destroyed though, it would all fall apart, because the replacement fighter would have a new name.