What type of airspace contains activities that may be hazardous to non-participating aircraft?

The type of airspace that contains activities which may be hazardous to non-participating aircraft is referred to as Warning Areas. These areas are established over international waters or in airspace that is not under U.S. jurisdiction and are intended to warn pilots of potential hazardous activities such as military exercises or testing. The primary purpose of warning areas is to provide information to pilots about potential dangers so that they can avoid these areas if they are not part of the ongoing activities.

Although other airspace types like Restricted Areas and Prohibited Areas also indicate activities that could be hazardous, they have specific restrictions imposed on them, where entry is either restricted (for Restricted Areas) or completely prohibited (for Prohibited Areas) to all non-participating aircraft. Military Operations Areas are also used for training and operations but typically do not have the same warning designation as Warning Areas, and they might not pose an immediate threat to non-participating aircraft, allowing for the possibility of transit. Hence, Warning Areas serve a distinct role in notifying pilots regarding potential hazards without imposing restrictions on airspace entry.