Controlled airspace above an airport that extends upward, vertically from the surface to a specified height AGL is?

The controlled airspace above an airport that extends upward from the surface to a specified height above ground level (AGL) is known as a control zone. Control zones are established to protect aircraft operating in the vicinity of an airport, especially in the approach and departure phases of flight. They help ensure safe and efficient air traffic operations by segregating various types of traffic and providing air traffic control services.

Control zones serve a crucial role in maintaining safety and order around busy airports, typically involving general aviation, commercial traffic, and sometimes military aircraft. The specifics of the dimensions and altitudes of control zones can vary based on the airport and are defined in aviation regulations.

The other options relate to different categories of airspace. For instance, while control zones often coincide with Class D airspace, they can also include segments of airspace classified differently depending on the specific operations surrounding individual airports. However, Class D is specifically defined by its operating regulations and does not encompass all control zones universally. Similarly, controlled airspace along airways or control areas have different definitions and operational regulations that do not specifically refer to the structure around an airport, making control zone the precise and correct choice in this context.