The fourth game in the series and the first to appear on the PlayStation 2, Ace Combat 04: Shattered Skies adds an intriguing narrative to the action-heavy dogfighting for the titles are known. A succession of 18 missions makes up the bulk of the single-player experience, placing players in the flight suit of an ambiguous pilot with a mysterious code name: Mobius One.Mission goals include destroying enemy forces, strikes on enemy installations, and everything in between. Some objectives are slightly more fanciful, requiring players to perform tasks such as intercepting nuclear missiles. Performance during a mission is rated, determining which extras are unlocked for future use.A total of 21 fighters are available, including well-known craft such as the F-14 and SU-37. Shooting down ace pilots (which is not usually part of the main mission objectives) will reward pilots with additional paint jobs for their fighter planes. With the planes of their choosing, two players can compete in head-to-head battles in a selection of levels. Once completed, players can replay the game using any of the planes they've already unlocked on previous play-throughs.