Ace Combat: Joint Assault takes a different approach, leaving the fictional worlds of previous Ace Combat installments and entering the real world. The missions take place over London, Tokyo and San Francisco, with fictional elements such as huge flying fortresses. The player takes on the role of a young pilot who joins the private military force Martinez Security and soon finds themselves fighting the Valahia, some sort of bandits which threaten whole cities - but the plot soon becomes more complicated.
The gameplay is mostly identical to its PSP predecessor. The player controls combat airplanes (either in third-person or from a cockpit view) and fights other airplanes (or other big flying enemies) while dodging their missiles. After completing missions, which mostly consist of killing a certain number of enemies or boss fights, the player receives money that can be reinvested into unlocking more airplanes or upgrades. These aircraft are based on real-life models and have advantages and disadvantages, such as some being more suitable against flying enemies while bombers are effective against ground targets. The mission tree is branching, and the player must choose between multiple missions at times.
The only major new features are the "enhanced combat view" (which gives a closer look at enemies during long-distance battles) and the co-op mode, which allows players to complete the campaign with other players. The game's branching missions divide players into two teams of up to four. Other multiplayer modes are similar to Skies of Deception , but allow eight players instead of four.