Location: Oslya
Requirements: 10 Oak Wood (5 Oak)
Enter 3rd cave from right (or 2nd cave from left depending on perspective).
Go left through the cave, then enter the northern exit. You'll emerge on a plateau where the crash cutscene will take place. Wright will ask you for a propeller and wings.
Once you have them, return outside and talk again with Wright and he'll give you the Mighty Plane Design. Now you can build the Mighty Plane.