The side air currents were continued to the rear, and used the natural sweep of the wood.
The end of the air flow was curved back toward the front to keep the viewer’s eyes moving around the piece.
The ribbons of air are starting to be separated to provide negative space. I think the ribbons of wood provide the information of the air’s direction of flow, and the negative spaces provide the information that the bird is passing through air.
I continued creating the lines, planes and negative spaces representing the air. As I see it, when a bird passes through the molecules of the air column, the molecules are wildly disturbed when the bird first passes. But after the initial disturbance, the air calms and is less disturbed as time moves on. So I try to create a lot of chaos where the bird is, but less where it has passed.