What is the special use airspace designated to confine activities hazardous to nonparticipating aircraft?

The special use airspace designated to confine activities hazardous to nonparticipating aircraft is referred to as a restricted area. These areas are established by the FAA to keep nonparticipating aircraft away from regions where there are activities that could pose danger, such as military operations or testing of munitions. Since the activities within these areas can include live fire exercises or high-speed maneuvers, access to restricted areas is limited to authorized aircraft only, which ensures the safety of both the nonparticipating aircraft and those engaged in the activities.

In contrast, while a warning area also serves to inform pilots of potentially hazardous activities, it does not restrict access; rather, it serves as a notice to pilots who might be flying in the vicinity. A prohibited area is even more stringent, as it completely forbids entry to all aircraft, but it specifically pertains to the most sensitive activities where no access is allowed. An alert area, on the other hand, is designated to highlight areas where there may be a high volume of pilot training or activities that require additional caution, but again does not limit access based on the potential danger level. Thus, the restricted area is the most fitting designation for confining activities that are specifically hazardous to nonparticipating aircraft.