What does a Class "C" or "D" Control Zone become after the tower closes?

When a Class "C" or "D" Control Zone tower closes, the airspace reverts to Class G uncontrolled airspace. This is an important aspect of airspace classification, as the rules for Class G airspace differ significantly from those for controlled airspace.

In Class G airspace, pilots are responsible for their own separation and must ensure they comply with visual flight rules (VFR) and other applicable regulations, as there is no air traffic control (ATC) service available. This transition is significant for flight operations and planning, as pilots must adjust their approach and navigation strategies accordingly once the control tower is no longer in operation.

Since Class E airspace denotes controlled airspace but still allows for some level of operational flexibility with ATC guidance, it does not apply when a tower closes, as there is no active control. Therefore, the correct characterization of the airspace in this scenario is Class G uncontrolled airspace, indicating that the area is no longer subject to ATC jurisdiction.