Most humans didn't fly really, so it was very interesting.

Trunks is observant enough, and following everything easily. She can see a type of gleam in his eye when she mentions testing limits, and speed. One she's probably seen in Rainbow Dash's eye, when a new challenge is placed before her. Asking for a pause, blue-eyes narrow in thought as he eyes the straight-away.

Before there is a small burst of energy and he's racing down it, focused, and alert. Gauging his own speed, but also trying to study how he's doing this. As it relates to using that chi to fly, and move through the air. It's...not the easiest thing, trying to relearn something that the body and mind clearly know how to do without thought.