When is airspace at an airport classified as Class D airspace?

Airspace at an airport is classified as Class D airspace specifically when there is an operational control tower present. The critical aspect here is the presence of the control tower, which indicates that air traffic control (ATC) is actively managing the airspace around the airport for the safety and efficiency of aircraft operations.

Class D airspace typically extends from the surface to a specified altitude, usually 2,500 feet above the airport elevation, and it is characterized by its requirement for communication with ATC. Pilots must establish two-way radio communication with the tower before entering this airspace, which is a defining feature of Class D regulations.

In this context, the other conditions mentioned do not classify airspace as Class D. Weather minimums being below basic VFR would generally indicate a restriction on flying under visual flight rules but does not influence the classification of the airspace itself. Similarly, the operation of a Flight Service Station (FSS) relates more to pilot services and information rather than airspace classification, as it does not independently dictate the presence or absence of controlled airspace.