What is one characteristic of Class D airspace?

Class D airspace is typically associated with airports that have an operational Air Traffic Control (ATC) tower. This characteristic is important because it indicates that there are specific communication protocols in place for pilots operating in this airspace. Pilots must establish two-way communication with the ATC before entering and while flying within Class D airspace, which helps manage the flow of air traffic around the airport. This controlled environment is essential for maintaining safety, especially in areas where there may be a mix of arriving and departing aircraft.

The existence of an operational ATC tower also implies that the airspace is at lower altitudes, generally extending from the surface up to 2,500 feet above ground level. This aligns with the purpose of Class D airspace, which is to provide a safe operating environment for both IFR (Instrument Flight Rules) and VFR (Visual Flight Rules) flights in the vicinity of airports. Thus, the connection of Class D airspace with operational ATC is a defining characteristic crucial for effective air traffic management in those zones.