I know the pattern of the mode "dogfight". Whoever has the same plane you have (axis, or Allie) you get a "traitors can be temporarily banned" message if you shoot the same type of plane you are. That's also why it says you win or lose, when, infact you didn't get 15 kills.
I hope this was helpful, see you in the skies,
Green Freedom
P.s. it only counts if you shoot their parachute. So try to avoid that.