In our technological world speed is far more important in air combat than agility, generally speaking. the classic example of this was in the Pacific in WW2 where once the Allies fielded fighters like the F6F and the P-38 and refused to dogfight with the agile Japanese aircraft like Type 0. Faster air superiority fighters can choose to engage or not to. There never seems to be enough of an agility difference to allow the slower aircraft to refuse an engagement by maneuvering out of the way.
I am not certain this will still hold true with flying creatures vs flying machines. The intrinsic ability of a flying animal to quickly change direction and to not have the time lag required by the man/machine interface.?
If creatures like Flying Lancers, Skrill riders, Bestial High Martians, the goofy critters from Pandora and suchlike can dodge and stunt their way away from aircraft will human-piloted aircraft ever be capable of effectively engaging them with fixed forward firing weapons? I can easily see things like the turrets on modern attack helicopters being very effective, but something like a Spitfire or P-51 might be at a serious disadvantage.