I have played quite a few games with external aircraft.grf's like AV8 or Planeset, but I really just wanted the default OpenTTD set, so I made them carry all cargoes, gave them good old TTOrig-like names and for commuter (small) airport - there are additionally the 727 and the enhanced Kelling K6.
Also gradual loading is more balanced.
Memorable aircraft and all helicopters were given a lasting availability (v2).