Final Fantasy XII: Revenant Wings Hints & Cheats

Beat the game with 100% mission cleared.

After chapter 4, you can unlock various objects to decorate your airship with. This makes your airship look better, and adds, not to the game completion score, but to your completion score.

NOTE:
In order to obtain and view the Supreme Crest, complete every single side mission before starting the Final Chapter (you should be on 97%).
After completing the first two levels in the Final Chapter, you should have 100% complete.
Create a new save file and then die during the boss fight. It will ask if you want to try again. Say no.
Go back to the airship and voila, you can apply the Supreme Crest to the airship! And then you have one save file for free exploring and one right before the boss battle!