"stalemate"
(pipes up; nb I am not a dogfighter)
Would the relative aircraft weights have any noticeable, or useful, effect, assuming in this case that both players have managed their fuel well, and that the difference is slight?
E.g. if the attacker took off with a reduced fuel load and drop tanks, which he has dropped, and the defender took off with reduced fuel, the two aircraft would have very similar but not identical weights (and there would be expended ammo to take into account as well).
In the long run one of the fighters would run out of fuel, especially if using WEP, which would break the stalemate. Although it would also be lighter than the other fighter, which might break the stalemate in the other direction.
It doesn't sound sportsmanlike to try and run the other man out of fuel, but then again this isn't cricket.