Which class of airspace requires special ATC clearance for operations?

Class B airspace is designated as the most controlled type of airspace, primarily surrounding busy airports, and it requires special Air Traffic Control (ATC) clearance for all operations within it. This designation ensures that aircraft can operate safely and efficiently in high-density traffic areas. The requirement for ATC clearance in Class B airspace helps manage the flow of air traffic, minimizes the risk of collisions, and facilitates the efficient use of airspace around major hubs.

In contrast, Class C airspace allows for some level of operations without needing clearance but requires pilots to establish two-way radio communication with ATC prior to entry. Class D airspace, while also controlled, requires communication with ATC but does not necessitate a clearance in the same way Class B does. Class E airspace, which is generally uncontrolled, does not require special clearance or communication with ATC unless weather conditions dictate otherwise.

Therefore, the requirement for special ATC clearance associated with Class B airspace is essential for maintaining safety and order in environments where aircraft operations are densely packed.