There is a bonus in place of a sort. If you simply continue the same sortie by refueling and rearming, your Kill # counter does not reset. So if I kill 2 planes with my Jug, then land and rearm/refuel and take off again and kill another plane, it will say "Kill #3 by Lephturn of The Flying Pigs". If I kill 2 planes, land and exit, get a new plane, then kill another one, it will have reset and I will get "Kill #1 by Lephturn of The Flying Pigs".
Think of it as part of the simulation. In real life, you would exit the plane and end your sortie while a crew repaired even minor damage and checked your bird over before the next sortie. However, you might land and refuel/rearm without climbing out if you were flying CAP for example. I think it works pretty well.
