By performing certain actions in Fit Mode, you'll unlock special achievements in the Results menu.

Achievement	How to unlock
Fit Mode Achievement #1	Clear Endless Off.
Fit Mode Achievement #2	Clear 100 planes.
Fit Mode Achievement #3	Clear 500 planes.
Fit Mode Achievement #4	Clear 1,000 planes.
Fit Mode Achievement #5	Clear 5,000 planes.
Fit Mode Achievement #6	Clear 10,000 planes.