Successfully complete arcade mode to unlock more levels in score attack mode.
To unlock all five of the original planes from Giga Wing, successfully complete the game on any difficulty setting with each character without continuing. The character you complete the game with will determine the plane that is unlocked. Complete it with Kart to unlock the Raijin, Romi to unlock the Purchka, Ralugo to unlock the Widerstand, Limi to unlock the Stranger, and Chery to unlock the Carmine.
Select the "Gallery" option from the main menu, then quickly press Up, X, Y, X, Down, Y, X, Y(2) at the first screen to unlock all planes, gallery entries, and two bonus options. If you entered the code correctly, you will hear a sound.