What do Visual Flight Rules (VFR) regulate?

Visual Flight Rules (VFR) are a set of regulations that govern how pilots operate aircraft in generally clear weather conditions. Under VFR, pilots navigate using visual references outside the cockpit, such as the ground and landmarks, rather than relying solely on instruments. This operational freedom allows pilots to maintain visual contact with the terrain and other aircraft, which is essential for flying safely in good weather.

The other options do not accurately represent the scope of VFR regulations. For example, pilot operations in bad weather conditions fall under Instrument Flight Rules (IFR), which are specifically designed for flights when visibility is low. Similarly, aircraft movements during nighttime operations can be conducted under both VFR and IFR, but specific limitations and requirements apply, and VFR is not exclusive to nighttime flying. Finally, aircraft maintenance checks are governed by separate safety regulations and are not part of VFR operations. Thus, option C correctly defines the foundational aspect of Visual Flight Rules.