> More seriously the solution suggested of giving the 3 companies other unused prefixes like D* U* and A* to use with their codeshares and non rev flights to st

> More seriously the solution suggested of giving the 3 companies other unused prefixes like D* U* and A* to use with their codeshares and non rev flights to start seems the easiest. That's exactly it. And what happens in merger situations where they keep operating some of the flights with the letters of the old companies The A* space seems full, the D* space is almost full though, U* has some space https://en.wikipedia.org/wiki/List_of_airline_codes https://en.wikipedia.org/wiki/List_of_airline_codes