Kill points are the damage you inflict on enemy planes (+1 single point for a kill). The more stuff you shoot up, the more kill points you get.
Isn't this one more complex---- where you get the multiplier?
Retain % of that sortie's kill points:
Landed = 100%
Ditched = 75%
Bailed = 50%
Captured = 25%
Death = 25%
Are you landing successfully after getting kills?
My understanding is getting 8 kills and dying is roughly equivalent to getting 2 kills and landing. Someone correct me if I'm wrong...