It seems luffy deflects his hands off air (like concrete) to change direction. We've seen his attack deflect off walls to hit targets, Enel for example, what's confusing now is how he does it with air.
I think
@Pro Ban Corps might be right, if one hits water or air at high enough speed, it treats it as some sort of solid or concrete. Sanji uses geppo or sky walk to treat air as solid in order to propel or lift his body.
By kicking air really fast, it seems as if it's a solid with a base, enabling him to jump even while in mid air. It's possible luffy's using the same technique, only this time instead of jumping, he defects his hand off it to the direction he wants, not sure I'm right though but it seems like that's what he's doing.