Which type of airspace primarily controls access to civilian air travel?

The correct choice highlights the concept of regulatory airspace, which is vital in managing and controlling air travel. Regulatory airspace refers to the areas where specific rules and restrictions are in place that govern air traffic, primarily to ensure safety and efficiency. It includes various classes of airspace, each with its own rules about who can fly there and under what conditions.

Regulatory airspace is designed to maintain safe distances between aircraft, particularly in congested areas, and to provide structured guidelines for navigation and communication. It encompasses several classifications, including Class A, B, C, D, and E airspace, and each serves to enhance coordination and safety among civilian air traffic.

In contrast, other types of airspace such as non-regulatory airspace, which lacks specific regulations, and military airspace, used primarily for military purposes, either do not manage civilian air travel or have limited control over it. Class B airspace, while regulatory, is just one segment of the broader category of regulatory airspace and primarily pertains to areas around busy airports, rather than the comprehensive control needed for all civilian air travel. Thus, the encompassing nature of regulatory airspace makes it the critical choice for understanding access to civilian air travel.