Air acceleration is the rate at which a character can change their horizontal velocity in midair. High air acceleration is advantageous for recovery and aerial combat, as it allows a character to reach their maximum air speed sooner and change direction more easily. Characters with high air acceleration do not necessarily have high air speed.
Air acceleration operates the same whether the character is attempting to speed up, slow down, or reverse direction. When the player is providing no horizontal input, air friction controls the character's rate of deceleration instead of air acceleration.
Air acceleration is controlled by two values: a base value that determines the minimum acceleration, and an additional value that is scaled based on how much the control stick is tilted. A character's maximum potential acceleration is the sum of these two values. For example, if a character has a base value of 0.01 and an additional value of 0.07, their acceleration can vary from 0.01 at minimum input to 0.08 at maximum input. It is most beneficial for a character to have a low base value with a high additional value, as this combination offers the most precise aerial control; a character with a high base and low additional would have a very limited range of possible speeds.
Air acceleration values
Note: By default, these lists are sorted first by total maximum acceleration, then by additional value in case of a tie.
In SSB, characters have a single maximum acceleration value instead of the later games' two-value system.