At which type of airport can you issue a circling approach?

The correct choice is a towered airport because circling approaches can only be conducted in airspace where there is active air traffic control. At a towered airport, controllers provide guidance and traffic advisories to pilots, which is essential for safely managing multiple aircraft operating in the vicinity, especially in the context of a circling maneuver. These approaches typically require coordination with the tower to ensure that flights can safely enter the traffic pattern and execute the circling maneuver without conflicts with other aircraft.

In contrast, non-towered airports typically do not have the same level of air traffic control oversight, making it difficult to safely coordinate circling approaches, as pilots must rely on self-traffic advisories and situational awareness alone. For military airports, while circling approaches may be applicable in certain circumstances, the regulatory context of a standard circling approach generally focuses on controlled environments, which are characteristic of towered airports. Emergency airports do not imply any specific operational capabilities regarding circling approaches, rather they are typically used in urgent situations and lack the infrastructure necessary for managing complex traffic patterns.