When is Class D airspace typically active?

Class D airspace is typically active when the controlling tower is open for operations. This type of airspace is established around airports with an operational control tower, and its purpose is to provide air traffic control services to aircraft operating in vicinity of the airport. When the tower is closed, the Class D airspace becomes inactive and the area generally reverts to uncontrolled airspace. Therefore, the activation of Class D airspace is directly linked to the hours during which the tower is staffed and managing air traffic, which makes it crucial for pilots and air traffic control to know when the tower is open for safe operations.

In contrast, the other options suggest conditions that do not accurately reflect how Class D airspace functions regarding tower operations.