For me its how aggressive they are and the timing of their maneuvers. I also look at how they merge and the way they approach me. 95% of the time I have to dodge a HO, so I know they most likely don't have the same timing as me after they miss. I typically roll one way and then the other to get them to miss the HO shot. If a player does that to avoid a HO, hes probably pretty good. If the player avoids the HO, and pulls a very hard emmilman, he probably is pretty decent. Are they getting flaps out quickly? Are they smooth in their rolls? Are they using throttle? These are very fast decisions and things to watch for to tell the relative skill level of the person you are fighting in the MA. The plane also has a big impact on what the player can get away with. I know for example, if i'm in a 109G14 and they are in a yak3, they wont be able to out roll me or out turn me no matter how good they think they are. That being said, I would fight the 109 in a yak3 assuming the player doesnt have the skill as me, as it's a very close fight. I might kill him even tho his 109 should technically out turn me. That's measuring skill and whether you think you have the skill to out turn them or not, even if your plane isn't as good. Planes do matter, so you do have to take that into consideration when fighting the opponent.