The following codes are used at the main menu screen:
Get $400 Million
R2, L2, R2, L1, R2, R1, R2, L1
Bonus Airplanes in N.GEN Mode
R1, R2, L1, L2, L2, L1, R2, R1
Unlock All Tracks and Aircraft in Arcade Mode
R1, L1, R1, R2, L2, R2, L2, L1
Beat both circuits of any type in first place to unlock a secret jet.
Thanks to Revolution reader Jodacky!