What defines Class D airspace?

Class D airspace is specifically defined as the airspace from the surface up to 2,500 feet above mean sea level (MSL) that surrounds airports with active control towers. The primary function of this airspace is to ensure safe operations for aircraft taking off, landing, and transitioning through the vicinity of these airports, where there is significant traffic.

This classification requires pilots operating in this airspace to establish two-way radio communication with the controlling air traffic facility before entering. This communication ensures that all parties are aware of flight intentions and can manage traffic efficiently, minimizing the risk of accidents and improving situational awareness.

The other options reference different classifications or attributes of airspace, but they do not accurately describe the defining characteristics of Class D airspace. For example, uncontrolled airspace and surface airspace with no communication requirements do not apply to Class D, as communication with air traffic control is a mandated requirement.