What type of aircraft must always have an operating transponder?

All aircraft operating in controlled airspace are required to have an operating transponder for several important reasons. Transponders serve as essential instruments that enhance situational awareness for both air traffic control (ATC) and other aircraft. They allow ATC to identify and track aircraft, ensure safe separation between them, and facilitate communication regarding altitude and flight information.

The requirement for a transponder in controlled airspace stems from the need for precise tracking and management of aircraft movements, especially in busy areas where air traffic density is high. In such environments, the risk of mid-air collisions increases, making the transponder's role critical for safety.

While various regulations apply to different categories of aircraft, including military and commercial operations, the blanket requirement for transponders in controlled airspace underscores their vital importance across all types of aircraft. Thus, ensuring that all aircraft flying in these environments are equipped with functioning transponders helps maintain safe and efficient air traffic management.