Ace of Aces was a series of five downloadable missions for Ace Combat 6: Fires of Liberation. These missions were re-imagined versions of campaign missions and designed to be extremely difficult. Ace of Aces missions had to be purchased from the Xbox LIVE Marketplace and could only be selected from the Free Mission menu next to the other difficulty options.
Each Ace of Aces mission increased the number of enemies and featured brand-new enemy formations and targets for the player to destroy. For example, "Invasion of Gracemeria" featured the P-1112 Aigaion physically present in the attack on Gracemeria and Victor Voychek piloting a CFA-44 Nosferatu, neither of which are present in the mission on any other difficulty. Ace of Aces also features several named enemy units not present in the main campaign, most notably former playable characters launching from the Aigaion in the final Ace of Aces mission. Due to the increased enemy presence, these missions consequently take much longer to complete than their lower-difficulty counterparts.
The Allied Support system is supplemented in Ace of Aces missions by a new Counter-Charge system.[note 1] At certain periods during each mission, a short timer will appear and enemy units named after colors ("RED", "GREEN", etc.) will start spawning. The player can destroy these units to raise the Allied Support gauge and summon allies that will join Allied Support requests. Higher numbers of allies will become available with the more colored units the player destroys, which will also boost the allied units' attack power.
The Electronic Support Measure (ESM) system is also modified in Ace of Aces missions. Enemy ESM—indicated by red circles on the radar—will continue to boost enemy units' attack performance, but they will now also lower the player's ESM level down to a minimum of -2. Negative ESM levels significantly reduce the player's standard missile homing performance and reload speed. The player can counteract this by switching to special weapons as they are not affected by negative ESM effects. Destroying an enemy ESM emitter will remove the red circle from the radar and restore the player's ESM level in that area.
- Invasion of Gracemeria: Defend Gracemeria from the invading Estovakian forces, including a naval force, airborne tanks, the P-1112 Aigaion, and Strigon Team, led by Victor Voychek flying a CFA-44 Nosferatu.
- Vitoze Aerial Defense: Protect Vitoze, the last remaining Emmerian stronghold, from the unrelenting Estovakian assault. In addition to bombers, Estovakia fields numerous attackers and helicopters as well as the two P-1114 Gyges.
- Sipli Field: Break through Estovakia's defensive line at Sipli Field with the help of the small number of allied units. Provide adequate air support and avoid taking damage from Estovakia's powerful SAM launchers. Finally, take down six members of Strigon Team all flying CFA-44 Nosferatus.
- Bartolomeo Fortress: Destroy the impenetrable Bartolomeo Fortress positioned in the natural defenses of Mount Marcello. Defend against the reappearance of the P-1112 Aigaion, supported by Strigon Team and the surviving members of the Belkan Air Force's Gault Team.
- Heavy Command Cruiser: Neutralize the naval fleet protecting the Aerial Fleet, shoot down all Gyges and Kottos support cruisers, and eliminate the ace pilots defending the Aigaion to shoot it down once and for all.
- Counter-Charge system (カウンターチャージシステム)