What happens to Class D airspace when the controlling tower is closed?

When the controlling tower at an airport with Class D airspace is closed, the airspace changes to Class E or Class E/G airspace, depending on the specific location and altitude limitations. Class D airspace is defined by the presence of an operational control tower, primarily meant to manage traffic around airports where this service is available.

Once the tower closes, the primary function of Class D airspace—providing controlled airspace services—ceases. At this point, the airspace typically transitions to Class E airspace, which is designed for less regulated flight operations. In some cases, particularly when below 10,000 feet MSL and in the vicinity of uncontrolled airports, it might become Class G airspace, which allows for VFR (Visual Flight Rules) operations without the need for air traffic control.

This transition is crucial for pilots as it affects how they communicate, navigate, and operate within that airspace, emphasizing the need for awareness of airspace classifications and their implications for flight operations.