

Probable kills are usually left out of the list. The Italian Air Force did not officially credit victories to individual pilots, but to their unit as a whole. The Soviets counted only solo kills, while group kills were counted separately, as did the Japanese. commands also credited aircraft destroyed on the ground.

British, Finnish and US air forces credited fractional shares of aerial victories, resulting in fractions, such as 11½, which might be for example 10 aircraft and three shares with the second pilot. Germans credited a shared victory to only one pilot, while the French credited full victory to all participants. It is not clear what impact each nation's rules for score crediting have on the counts listed below. Additionally, national policies differed German, Italian, and Japanese pilots tended to return to the cockpit over and over again until they were killed. Towards the end of the war, the Axis powers had largely exhausted their supply of skilled pilots and the replacements did not have as much opportunity to gain enough experience to be successful. Fighter aces in World War II had tremendously varying kill scores, affected as they were by many factors: the pilot's skill level, the performance of the airplane he flew and those he flew against, how long he served, his opportunity to meet the enemy in the air (Allied to Axis disproportion), whether he was the formation's leader or a wingman, the standards his air service brought to the awarding of victory credits, et cetera.
