Find a video of skydivers performing the "delta" maneuver.
This is a body lift glide, like flying a wing suit without the wing membranes. Push a human body forward at around 100+ mph, and the airflow over the torso and legs (in Earth's atmosphere) can generate enough lift to support the body. Obviously, when skydiving, this doesn't equal level flight; considerable downward velocity is still required to keep the speed high, but in delta, a skydiver can travel horizontally at around a third of their vertical fall speed.
Now, give the skydiver rocket boots (and this has been done, with micro turbojets and wing suit, though not as far as I know for a no-membrane delta) and the vertical fall can be eliminated. Minimum flight speed would be close to 120 mph, but since Quill's boot jets can lift his weight against at least 1G and don't appear to require large fuel tanks, I see no reason he couldn't maintain this speed as long as necessary.