At the Aircraft Selection screen, press Square, Circle, L1, R2, Select.
Auto Gyro
Successfully complete all levels in sky canvas mode with more than 90 points to unlock the Auto Gyro.
Corsair
Accumulate enough acrobatic points in adventure mode to have ten of your mission grades marked with circles to unlock the Corsair.
Custom parts
Successfully complete all adventure mode levels with at least a B rank to unlock custom parts.
Gold UFO
Successfully complete all levels in target mode with a gold rank to unlock the Gold UFO.
Level Select
At the Mission Selection screen, press X, Triangle, R1, R2, L2.
Me-262
Successfully complete adventure mode to unlock the Me-262.
Pontoons
Successfully complete the Stormy Seas level in adventure mode by landing on an aircraft carrier. The pontoons will allow your aircraft to land on the water.
Shinden parts
There are 4 total Shinden parts hidden in adventure mode. To get these parts, you have to find the alternate landing strips and land there. As with the Swordfish wing, you can find the strips more easily if you first unlock the Special Radar in target mode.
Fuselage: The Towers Of Terror alternate landing strip.
Jet Engine: The Great Divide level alternate landing strip.
Right Wing: The Adventure Begins level alternate landing strip.
Left Wing: The Labyrinth level alternate landing strip.
Silver UFO
Successfully complete all levels in the adventure mode with an A rank to unlock the Silver UFO.
Stealth Fighter
Successfully complete all levels in adventure mode with a total time of 10 minutes or less to unlock the Stealth Fighter.
Swordfish third wing
Land at the Mid-Air Rendezvous alternate landing strip in adventure mode to find a special third wing that attaches to the Swordfish. With this wing the Swordfish converts into a tri=plane. If you unlock the Special Radar in target mode first, you will find the landing strip more easily.