Awful. That's the best I can say about this.
No way a P-40 outperforms a Bf 109 G, the stunts pulled are past ridiculous (The guy puts his throttle to zero, pulls a tight loop and get's behind his enemy and the loop was not even 10 meters wide). The dog fighting scenes are also ridiculous and almost like space jet combat (No wonder though, considering it's a george lucas movie). And like others pointed out, in reality one 30mm shell from that 262 would've shredded the P-51 but in the movie it just put small holes in it and it took several 30's to kill a pilot while in reality one would be enough to blow a person up.
The whole film is filled with clichê lines and too much small talk and over the line racism (Yes, they suffered from racism then but it was not as much as they make it out to be).
If I could I would give it a zero star but google doesn't allow that... All in all, that's 2 hours and 5 minutes of my life down the toilet.