In the game's campaign mode, the player plays the role of the flight lead in Gryphus Squadron, of the Aurelian
Air Force. The game is broken down into missions which involve various combat objectives, such as attacking
ground targets,
air targets, or a mix of the two. The "Free Mission" mode allows levels unlocked in the campaign mode to be replayed to achieve a higher rank or gain points for the purchase of planes or equipment.
Ace Combat X also includes a multiplayer mode, using ad-hocwireless to connect up to four players. The game is a mix of
arcade action and
flight simulation, making it semi-realistic. The player can choose from many real planes and over ten fictional planes, where the more advanced planes have to be unlocked first. The player can choose from variety of different viewpoints, including a third-person behind the plane perspective, and a first-person view that can be displayed from within the
cockpit (showcases the interiors of all the planes in the game) or simply with a
HUD.
Unlockables and credits In single-player mode, new planes, medals, weapons, parts, paint schemes and bonus missions can be unlocked, where they can be purchased in the hangar afterwards. At the completion of each mission, a rank and points are awarded based on the completion time and enemies destroyed. They can be used for the new planes, special weapons or the unique unlockable parts which can change the performance and stats (Speed, Air-to-Air, Air-to-Ground, Mobility, Stability, and Defense). Medals are awarded for meeting certain conditions in either campaign or free mission mode, such as providing damage or destroying a number enemies. Each mission or level also contains a "star" unit and an "ace" unit. Destroying the star unit unlocks weapons and equipment, while defeating the ace unlocks a paint scheme.
Missions The player can choose their own route through the campaign, which affects how the game progresses. There are points where missions branch out into multiple paths, marking segments of the game. By choosing which missions to take on, players can shape the course of the missions that are being played after by triggering or not triggering certain events (shorter time limit due to limited fuel or removing enemies that could have appeared otherwise). Certain bonus stages are also unlocked by taking a particular campaign path. Most of the missions in the game are laid out as simply "
search-and-destroy", where the player must engage a target and destroy it within a time limit; the only variations to this layout is whether the targets are air-to-air or air-to-ground (land or sea). There are four levels of difficulty: Easy, Normal, Hard, and the unlockable Ace level. The difficulty mode affects how many enemies are in a stage, how accurate the enemies are, how much damage the enemies and the player's airplane can take. ==Plot==