Doubleflight

Doubleflight (ダブルフライト) is a technique introduced in Kingdom Hearts Birth by Sleep. It allows the user to leap higher by means of a second jump.

Mechanics
In Kingdom Hearts Birth by Sleep, Doubleflight is a exclusive to Aqua that is activated by pressing,  in the Japanese versions, while in mid-jump. It has a maximum level of 1.

In Kingdom Hearts 3D: Dream Drop Distance, Doubleflight is a exclusive to Riku that is activated by pressing  while in mid-jump. In Kingdom Hearts Dream Drop Distance HD, Doubleflight requires pressing, in the Japanese version.

In Kingdom Hearts 0.2 Birth by Sleep -A fragmentary passage-, Doubleflight is activated by pressing, in the Japanese versions, while in mid-jump.

In Kingdom Hearts III, Doubleflight is a mobility ability that costs 2 AP to equip and is activated by pressing, in the Japanese versions, while in mid-jump. Doubleflight can be stacked to increase the height covered.

Kingdom Hearts Birth by Sleep

 * Aqua obtains Doubleflight after encountering Captain Hook in the Gully.

Kingdom Hearts 3D: Dream Drop Distance

 * Riku can obtain Doubleflight from a chest at the Delusive Beginning.

Kingdom Hearts 0.2 Birth by Sleep -A fragmentary passage-

 * Aqua obtains Doubleflight after finding the gear on a rooftop in Castle Town.

Kingdom Hearts III

 * Sora obtains Doubleflight after defeating the 3 Frost Serpents in Arendelle.
 * Element Form has Doubleflight as a form ability.
 * Riku has Doubleflight as a default ability.
 * Aqua has Doubleflight as a default ability.

Kingdom Hearts III Re Mind

 * Roxas has Doubleflight as a default ability.
 * Kairi has Doubleflight as a default ability.

Trivia

 * In Kingdom Hearts III, of all the playable characters, Sora is the only one who does not summon an ethereal platform of magic under him when he uses Doubleflight. Instead, several wind trails fly up from him.