I can get through the first 2 parts of this easily but when I have to kill 20 planes in a few minutes its impossible for me. They are always on me, I cant get around on them. I tried using different planes to no avail. Am I doing something wrong? I have to kill all the red planes on the radar correct? I can get them down to 3 or 4 left but never better then that. I had no trouble with the rest of the game and beat each other level on first try.

any help is greatly appreciated.

I had difficulty with this mission as well.
To protect Midway Island air strip, you have
to get into attack mode and signal FRANK to help
you out. Skillful airial manuevering is required. Try pressing the A button to find the next objective target to speed things up.
For the clear the skies of enemy aircraft checkpoint, you will need to constantly keep in
attack mode, use Frank and skillfull manuevers.