Level select:
Press C-Up(7) when "Press Start" appears on the opening screen.

Debug mode:
Hold Z and press Right, Left, Up, Down, A, B, Start when "Press Start" appears on the opening screen.

Shoot down the President:
Press Z + C-Up + C-Down during game play, then fire a homing cluster at an enemy plane.

Power chopper:
Hold L + R + Z and press Start at the main menu before selecting a chopper.

Chopper preview:
Highlight a chopper on the chopper selection screen. Press L to display the statistics screen. Press the Analog-stick to control the rotating model of the chopper.

Alien weapon:
Complete level 7 under the expert difficulty level. Then, fight on the moon to purchase the alien homing plasma weapon.

King 10:
Locate King 10 in level 7, defeat him, then complete the mission.

Stingray:
Locate Stingray in level 7, defeat him, then complete the mission.

Hint: Defeating the level 6 Boss:
Fly under the large green plane at the end of level 6. Shoot the large green missiles up into the plane for an easier battle.