Secret Modes - Start the game and go to an area on the map with no enemies. Hold START and Press A, B, C, B, A, A, B, C, B, A, B. Let go of START for invinciblity, hold A for fight ace, hold B for the mothership and hold C for the last Boss. Continue to hold as designated while you leave the hanger. Once the round begins, let go of the buttons.

General Secrets
On the mission select Screen, move the crosshair to a
place on the map that's not an area. Hold down START and press
A B C B A A B C B A B. Release START and you'll hear a soft ping. Now
move the crosshair to an area you wish to attack and hold down START to be
invincible, A to square off against the Fighter Ace, B to fight the Super
Carrier, and C to go right to the Last Fighter. You have to hold down the
until the area begins. Note that you can hold down START with any of the
others; for example, hold down START and C to take on the Last Fighter and
be indestructible.