Different Paintjob- To choose your alternate paintjob in main game, practice or boss mode, press the R button at the plane select screen. To select the alternate color in Death Match, hold the R button while selecting one of the four original planes.
Mao Mao- To activate Mao Mao and his F-15J Eagle, press C Left, C Down, C Right, C Up, C Left, C Right then C Down on the main menu. (He'll also appear if the game is continued more than three times on the Tokyo stage).
Spanky the Dolphin- To get Spanky and his X-29A, complete all the bonus stages. (See Below)
New Ship- To get a new ship press C-left, C-down, C-right, C-up, C-left, C-right, C-down at the press start screen. To get a new paint job on the planes press the Top-Right button on the plane selection screen.
Bonus Plane- At the "PRESS START" screen, press C-Left, C-Down, C-Right, C-Up, C-Left, C-Right, C-Down.
Extra Pilot- On the title screen, NOT the main menu screen Press Start. Then press the following buttons: C-Left, C-Down, C-Right, C-Up, C-Left, C-Right, C-Down. Don't be discouraged when you don't hear a sound or see something new, because nothing will happen. Go to any plane select screen, and on the far left, you will see a new F-15 plane with a girl pilot.
Enemy Planes in the DeathMatch- After beating each level you will enable another plane in the deathmatch. There are 6 total.
Bonus Levels:
Air Docking- To access this level you must beat Tokyo and the Pacific Ocean with a very high score.
Shuttle Defense- You must beat Tokyo, the Pacific Ocean, and the Air Battle with a very fast time. (NOTE: An easy way to quickly beat the air battle is to use your boost at the start and get behind the main plane and then use your brakes as you approach the back of it so you have more time to fire at it. Keep making passes at it untill its destroyed. Try not to put to much focus on the smaller planes).
Goliath Defense- This level is accessed after the fortress, if you've beaten the first 2 bonus levels already.
Extra Stage- You can access this final level if you've beaten all the stages including all the bonus levels.