K/T is a "problematic" score now measured in seconds, milliseconds or nanoseconds.
As an example, you takeoff, use five mins to fly to the combat area, then expend other five mins fighting getting 3 kills and other 5 mins returning to your base.
The problem is that if you keep in the combat area untill fuel is gone, you probably will double your kills, you will have much better kills per time, better or same kill/sortie and same ammount of points while keeping a more than decent kill/death ratio.
IMO, K/T should be considered only when you end your sortie landed in a friendly field. Else, the expended time is considered but not the kills achieved (only for K/T ratio).