Air Jump is an evasive airbending ability that launches you into the air on your next jump. Wherever you are looking is where you will be launched towards. The ability can be enhanced to make you jump even higher.
As with all other abilities, there are two choices for Air Jump's level IV upgrade.
Double-jump: Allows you to make a double jump but costs double chi
Double-jump is a good upgrade because it adds more mobility to the jump. It allows you to be more elusive and quick at escaping and/or repositioning. If the airbender likes to move freely in the air, this upgrade is recommended.
To proc the second jump you need to re-activate the ability mid-air.Ground pound: Attack nearby enemies on land
This upgrade adds a cool feature to the ability. After landing you damage entities near you, which adds an offensive factor to this utility ability. If you, as an airbender, want to use this ability to engage, you should follow this path.