spitfires, beaufighters and YAK-9 are the 3 most OP aircraft ingame IMHO. it looks like everyone is flying one ...
Spitfire Mk. IX is the most OP plane in the game as it has no other weakness than it's roll rate, but even that one is still moderate and serves the job. It outclimbs everything, it turns better than anything and it is much faster than anything. Next plane on the list might be the Chaika. This plane is so ridiciolous nonesense in this game, it is a complete joke.
The problem is that the Spity Mk. IX is a tier 10 plane and yanks get it as a premium plane on level 5. I see only freaking premium Spitfires since the last big patch and that's the thing that will keep me away from this game. Because that's the step when they turn the whole game into pay-to-win. This plane is literaly spoken a one-man-army.
You can deal with Beaufighters and Yaks fairly easy btw, atleast in HB. People who judge planes after their performance in AB have no clue what they are talking about tbh. This game mode has no proper physics implemented and you can do anything with a plane, no matter whether it is physical correct or not. You will never have to think about your ammunition, landing speed, when your wings will get ripped off or the strength or weakness of your plane in general. The only thing that matters is the size of the gun. In HB the yak 9t is quite a challenge to fly as you only have 30 rounds of cannon shots that you have to use very careful and the flying abilities are not that good either, atleast not compared to the other planes on that level ... we are talking about Bf109's and Spitfire Mk IX.
Yaks have crappy climb rates aswell as the Beaufighter. If you consider those planes as OP then I don't know. Alt-advantage is all that matters in this game, as you can transfere it into speed. Heavy fighters are planes that require alot of team work as you can't climb into nowhere, otherwise you are pretty fucked when the fighters dive down on your tail. Beaufighters have still good turn rates, but that's a different problem as mentioned before.