Various Codes
Before the "Now Loading" screen with the bird logo comes up, press and hold R1+O. This will change the "Now Loading" screen to bouncing CD's. Now you can enter any of the following:

Change your own plane color - While the bouncing CDs are showing, UP, DOWN, LEFT, RIGHT, UP, DOWN, LEFT, RIGHT, then R1. Watch for a Namco character at the lower left for confirmation.

Change wingman's color - Press RIGHT (keep it pressed) and press START 10 times. Look for confirmation again.

Play a short hidden game - Press UP, LEFT, DOWN, and RIGHT. A small character icon will appear in the lower left of the screen. Now the next time there is a loading game, don't press the R1 and 0, and the game will pop up.

999,999,000 credits - Press Down, O, T, T, T, O, T, O, T, then press O+T simultaneously twice and hold both buttons down after the second press. You should see a Pooka from Dig Dug in the corner of the screen. Start the game and you'll have 999,999,000 credits!

Extra wingmen - Hold R1 and press START 10 times. Continue to hold START after the 10th press.

Skip mission overview (Japanese version)
Press Triangle and Start.

Remove captions (Japanese version)
Pause game play, press L1 or R1, and resume the game. The Japanese text on the right side of the screen will disappear.

Wingmen
Wingmen can draw enemy fire and planes during a mission. Choose a veteran wingman in a fast plane. Rhio in the F/A-18 is a good combination.