Kill Rate (キルレート) is a gameplay element that records the player's usage of an aircraft, typically through the number of points they earn. It was introduced in Ace Combat 5: The Unsung War as a method to unlock aircraft through a rudimentary technology tree, and it has subsequently appeared in handheld games to unlock liveries and special weapons.
Ace Combat 5: The Unsung War
Some aircraft in Ace Combat 5 are locked behind other aircraft. The player must complete an aircraft's Kill Rate bar to unlock the aircraft behind it, by completing missions in campaign and Free Mission to earn points. Earning higher Clear Ranks and completing minigames will award bonus points, which also count for the Kill Rate. Every aircraft has a different threshold for their Kill Rate bar.
In addition, the player's difficulty when completing a mission will apply a modifier to the points they earn for the Kill Rate bar. Easier difficulties will make it harder for the player to complete the Kill Rate. The modifiers are as follows:
- Very Easy: x0.25
- Easy: x0.50
- Normal: x1.00
- Hard: x1.25
- Expert: x1.50
- Ace: x2.00
Because of these modifiers, it is highly recommended to play Free Mission on Ace difficulty to earn the most points possible. The Ace Combat 5: The Unsung War Perfect Guide also specifically recommends replaying The Unsung War, since it has the fewest enemies and a relatively high point reward.
Ace Combat X: Skies of Deception
In Ace Combat X: Skies of Deception, Kill Rate is solely used to unlock an aircraft's Special 2 skin. Only points acquired through defeating enemies count towards Kill Rate in Ace Combat X; Clear Ranks and minigame bonuses do not apply.
Ace Combat: Joint Assault
Ace Combat: Joint Assault uses Kill Rate similarly to Ace Combat X; it is exclusively used to unlock alternate aircraft skins. Only points acquired through defeating enemies count towards Kill Rate in Joint Assault.
Each aircraft in Joint Assault has five alternate skins. Color 02 is unlocked by completing 20% of an aircraft's Kill Rate; Color 03 is unlocked after completing 40%; Color 04 after 60%; Color 05 after 80%; and Color 06 after 100%. The only exception is the 747 200B, which cannot destroy enemies. The player must sortie repeatedly in the 747 to unlock its alternate skins.
Ace Combat: Assault Horizon Legacy
In Ace Combat: Assault Horizon Legacy, the Kill Bar is now the Kill Rate Gauge, but serves the same purpose as Joint Assault, unlocking the next paint scheme. However unlike in Joint Assault, paint schemes are unlocked in this order:
- Ace Combat 5: The Unsung War Perfect Guide, page 059.
- Ace Combat 5: The Unsung War Perfect Guide, page 177.
- Ace Combat X: Skies of Deception - The Complete Guide, page 040.
- Ace Combat: Joint Assault Perfect Guidebook, page 042.
- Ace Combat: Joint Assault Perfect Guidebook, page 149.