Except for the arc spreader, which I used in almost every battle, the other weapons suggested are crap. Lightning, Short Shield, and Duck. Short Shield is king of taking out turrets.
You don't need elaborate buy schedules to do it, just tips:
-go for the glider asap
-you don't have to finish each ramp to move on, go for height and fly time to get the award, then move up
-go back to the previous ramps when you have upgraded and you can get the speed and distance awards easily
-try to fly horizontal as much as possible, using rockets to keep as high a speed as you can, without going into the red.
At least, that is how I did it.
uhhhh, i agree with solistus. this game is not that fun, really. just a bit more effort into it could make it shine, i guess, but the game as is just doesnt hold my attention...
 "Super Epic RPG"){kind=icon}
 "Infectonator!"){kind=icon}
 "Heavy Weapons Guide"){kind=icon}
 "Learn to Fly"){kind=icon}
 "Black Navy War"){kind=icon}
 "Crush the Castle"){kind=icon}
 "Epic Battle Fantasy"){kind=icon}
 "Mechanical Commando"){kind=icon}
 "Doom 1"){kind=icon}