Definitely the best of its kind.
Most plane fighting games tend to be a bit slow in the sense of being fun and challenging. However, this game certainly breaks the stereotype! It was a bit challenging at parts and had great level variation. I loved the simple yet suiting graphics, and the sounds were pretty nice. The enemy AI was actually pretty challenging, especially the aces. The only thing I would suggest if you make a sequel is to make the plane animation a bit better. Like, instead of flying upside-down when you go left, maybe you could make the plane roll over to fly on the right side. Also, more levels! Maybe you could add some more unique features like more mission types. Instead of the beat the enemies forces, you could maybe have a raid on a German fuel dump or something.
Anyway, great game, and I really hope you make a sequel!