What distinguishes Class D airspace from Class C airspace?

Class D airspace is characterized by a smaller radius and is generally less complex compared to Class C airspace. Specifically, Class D airspace typically has a vertical limit from the surface up to 2,500 feet above ground level, extending usually up to about a 4 nautical mile radius from the airport. In contrast, Class C airspace has a larger radius, generally extending out to 5 nautical miles, and includes additional airspace above it, requiring more sophisticated air traffic control services and communication.

The simplicity of Class D airspace means that it often serves airports with an operational control tower but does not require the same level of aircraft separation services as Class C airspace. This distinction is key for pilots in understanding the operational environment they are entering, as the requirements for communication and navigation differ significantly between these classes.