What defines a controlled airport?

A controlled airport is specifically defined by the presence of an operating control tower. This control tower plays a crucial role in managing air traffic and ensuring safe operations within the airport's vicinity. The air traffic controllers stationed in the tower provide critical instructions and guidance to pilots, helping to coordinate departures, arrivals, and ground movements. This structured environment is essential for maintaining order, especially at airports that experience high levels of traffic.

Other aspects related to an airport's size, services, or primary use do not inherently designate it as controlled. While large runways can accommodate various aircraft types, and cargo operations are important, neither of these characteristics determines whether the airport has an active traffic control system in place. Similarly, the absence of flight services does not influence the classification of an airport as controlled or uncontrolled. Thus, the defining element of a controlled airport is indeed the operating control tower.