Ace is the highest difficulty in Ace Combat 8, but it isn't available when you first start the game. You have to clear the campaign on Elite before it becomes selectable, so players planning an Ace run will need at least one full campaign completion first.

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How to Unlock Ace Difficulty in Ace Combat 8

To unlock Ace difficulty, complete all 30 campaign missions on Elite difficulty. You do not need to earn an S Rank on Elite, defeat every named Ace, or complete any separate challenge. Reaching the end of the campaign on Elite is the unlock condition.

Ace Difficulty Unlock Requirement
• Select Elite difficulty
• Complete all 30 campaign missions
• S Ranks are not required
• Ace difficulty unlocks after the Elite campaign clear

If Elite is your first playthrough, you can therefore go straight from finishing the story into an Ace run without completing another difficulty in between.

Veteran and Lower Difficulties Do Not Unlock Ace

Finishing the campaign on Rookie, Pilot, or Veteran is enough to complete the story, but it does not satisfy the requirement for Ace difficulty. The unlock specifically requires an Elite campaign clear.

That doesn't make a lower-difficulty first playthrough useless. Finishing the campaign opens Free Mission and lets you build out your aircraft, parts, weapons, and MRP before attempting Elite. If Elite is giving you trouble with an early-game hangar, doing a normal campaign clear first can make the required Elite run considerably easier.

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Do You Need S Ranks on Elite to Unlock Ace Difficulty?

No. Your mission ranks on the Elite playthrough do not determine whether Ace unlocks. You only need to finish the campaign on Elite.

This is worth separating from the Ace of Aces trophy or achievement, which has a much stricter requirement: all 30 missions need an S Rank on Ace difficulty.

In other words, don't restart an otherwise successful Elite mission just because you finished with an A or B Rank if your only goal is unlocking Ace. Clear the mission and keep moving toward Mission 30.

Can You Play Ace Difficulty in Free Mission?

Yes. Once Ace difficulty has been unlocked, you can use it when replaying missions through Free Mission as well as when replaying the campaign.

Free Mission itself unlocks from completing the campaign, regardless of difficulty. If your first clear is on Elite, both milestones happen as part of the same playthrough: finishing the campaign opens Free Mission, while completing it specifically on Elite adds Ace difficulty.

This is particularly useful if you're eventually going for S Ranks. You don't have to repeatedly play the entire campaign from beginning to end just to improve individual mission results.

What to Do After Unlocking Ace Difficulty

If you're only interested in playing on the hardest setting, you're done as soon as the Elite campaign clear registers. Start a campaign replay on Ace or select Ace when entering an available mission through Free Mission.

If you're going for Ace of Aces, unlocking the difficulty is only the first step. You then need an S Rank on every campaign mission while playing on Ace.

I wouldn't combine those two goals mentally during the Elite run. Use Elite to get Ace unlocked, improve your hangar along the way, and learn the missions. Then worry about the much more demanding score and time requirements once you're actually playing them on Ace.