Three Planes and Bonus Mission:
After you complete level ten, go to the mission select screen, look to the right of 
the screen, and there will be a tiny airplane. Click on it and there will be a sound 
to confirm the code. Now you have access to three new aircraft, including the 
U.F.O., the F-22 Raptor, and the Kikka, a Japenese plane. You will also be able to 
unlock mission 11, a bonus mission.