The following modes and more can be unlocked by performing the actions below.

Complete 13 Plane Arcade Mode - Arcade Stage Select
Complete 13 Plane Arcade Mode - Extra Stage Select
Complete 13 Plane Arcade Mode or 13 Plane Extra Mode - Rate Viewer
Complete Arcade Mode - R-Gray 0
Complete Extra Mode - R-Gear Rollout
Continue the game 50 times. - Unlimited Credits