Ace Combat 5: The Unsung War Cheats

Upon completing every mission on the Ace Difficulty while obtaining an "S" Rank, you'll recieve a special message from the developers during your final debriefing.

In mission 16A "Desert Arrow", the ground is mostly desert with lots of circular patches of green (farmland, I suppose). One patch is in the shape of a Pac-Man ghost. To find it, go to grid section 5D (upper left grid is 1A, with numbers going across and letters going down). It's in the northern middle section of the grid.