Difficulty is an optional gaming scale affecting several in-game aspects in one's game. Difficulty settings are well known throughout the gaming industry, and Ace Combat features many different difficulty settings and effects.
In respective order from easiest to most challenging, most Ace Combat games have the following difficulty settings:
- Very Easy: Suitable for first-time players.
- Easy: Suitable for inexperienced or novice players.
- Normal: Suitable for average players.
- Hard: Suitable for advanced players.
- Expert: Unlocked by beating the game on Hard. Suitable for Ace Combat specialists.
- Ace: Unlocked by beating the game on Expert. Suitable for true Ace Combat veterans.
Some Ace Combat games do not follow this pattern. For example, all of the games up to and including Ace Combat 3: Electrosphere only feature Easy, Normal, and Hard. The handheld titles only feature Easy, Normal, Hard, and Ace. Ace Combat: Assault Horizon also only features these four, but renamed Easy to Rookie, Normal to Pilot, and Hard to Elite.
Ace Combat 6: Fires of Liberation features a downloadable mode known as Ace of Aces, which is not to be confused for a difficulty mode; rather, it features modified versions of certain campaign missions.
The difficulty the player chooses will alter several aspects of gameplay. Difficulty generally affects the following aspects (actual effects vary on a per-game basis):
- Damage taken: On Expert and Ace, most of the players' planes will be lucky to survive one missile hit, while on Very Easy more advanced planes can very well take ten missile hits before exploding from damage.
- Ace Combat: Assault Horizon: On all difficulties except Ace, planes automatically repair and lose their damage status. The tougher the difficulty, the slower the repairs. However, on Ace, plane damage does not repair, and the amount of damage saves at checkpoints.
- Enemy performance: On tougher difficulties, enemies may be more evasive and aggressive, being harder to hit and attacking the player more actively.
- Enemy plane strength: Tougher difficulties may make enemy planes more resilient, requiring more damage to take them down. This mostly applies to the games up to and including Ace Combat 04: Shattered Skies.
- Enemy composition: Higher difficulties may spawn additional enemies and/or change the location of specific targets. This is common practice in the series regarding the spawning of named aces; otherwise, this notably applies to various missions in Ace Combat 6, with some minor occurrences in Ace Combat 2 and Ace Combat Zero: The Belkan War.
- Player ammo:
- Missiles: On Very Easy, planes have far more than enough missiles to complete the mission, while tougher difficulties will require more careful use of a player's limited missiles.
- Machine Gun: In games where machine gun ammo can be limited, it tends to apply only in the higher difficulties, while lower ones provide infinite ammo. Ace Combat 04 is a notable exception, where gun ammo is limited on all difficulty settings.
- Aircraft repair: In games that feature a Return Line, the player's aircraft will not be repaired when using it on Expert and Ace difficulties. The same applies to Ace Combat 6's frontline landings.
- Anti-crash assistance: In certain games, lower difficulties will allow the player to survive crashes with the ground or large aircraft, only receiving damage instead.