Final answer:
The subject of this question is Physics. The FAA regulations regarding cruising altitudes for VFR flights fall under the domain of aviation physics.
Step-by-step explanation:
The subject of this question is Physics. The Federal Aviation Administration (FAA) regulations regarding cruising altitudes for VFR flights fall under the domain of physics, specifically aviation physics. Aviation physics deals with the principles and laws governing the motion and behavior of aircraft and is essential in ensuring safe and efficient air travel.