Body left/right direction transits!
When you have mastered flying on your back and on your belly, you can perform a transit from belly to back and back to belly. Pay attention to how I do it. When transitioning from belly to back, I use my hand - I lead with it, and my body follows. When I’m on my back, I start with my leg, and my whole body follows its movement.
However, this is not the only way to do it. This is just one of the ways you can perform this transit.