Ace Combat Xi: Skies of Incursion was the only iOS game in the Ace Combat series for Apple devices (iPhone, iPod Touch, and iPad). It was released on December 3, 2009 through the App Store. It received updates sporadically, mostly to add more aircraft. The plot of Ace Combat Xi followed the Aurelian Air Force Falco Squadron during the opening stages of the Aurelian War as Leasath begins its invasion of Aurelian territory. Xi serves as a prologue to Ace Combat X: Skies of Deception, which had started off mid-way through the war after Leasath had defeated most Aurelian forces.