Full power:
Pause game play and press [Up, Down, Left, Right] three times, II, I. Note: This code may only be enabled once per game.

Bonus ships:
Pause game play, hold Up and press II, I, I, II. Then, hold Down and press I, II, II, I.

Level select:
Hold II and press Run ten times at the "Formation Select" screen Use Left or Right to select the starting level.