During the Usean Continental War in Ace Combat 04: Shattered Skies, 18 Erusian aces were engaged and shot down by Mobius One. The majority of these aces came from the Federal Erusian Air Force but some may have been members of the Federal Erusian Navy's naval air force. The aces only appear during the second and following playthroughs of the campaign (via SP New Game), as well as in the Free Mission mode (unlocked after the first playthrough). They only appear on Normal difficulty or above. They do not appear on the radar unless the player is close to them.