What is the designation for airspace where flight may be subject to special restrictions but not completely prohibited?

The correct designation for airspace where flight may be subject to special restrictions but not completely prohibited is a Restricted Area. In such airspace, specific activities such as military training, high-speed maneuvers, or other operations that could be hazardous to other aircraft take place. While pilots can fly through a Restricted Area, they must obtain permission from the controlling authority. This ability to access the airspace, albeit with limitations, is what distinguishes it from Prohibited Areas, where flight is entirely forbidden.

In contrast, Prohibited Areas are off-limits to all aircraft, and entry is usually strictly enforced. Alert Areas are designated to notify pilots of a high volume of pilot training or unusual aerial activity, but flights are not restricted within these areas. Military Operations Areas (MOAs) can also be active with military training activities, but they allow civilian pilots to operate freely, though it's advisable to exercise caution and be aware of the potential for military traffic.