What requirement exists for aircraft operating at higher altitudes in controlled airspace?

Aircraft operating at higher altitudes in controlled airspace are required to be equipped with a transponder that has Mode C capability. Mode C transponders provide important altitude information in addition to the aircraft's identification. This capability ensures that air traffic controllers can receive accurate real-time altitude reports, which are essential for maintaining safe vertical separation between aircraft. This requirement is particularly critical in controlled airspace where traffic density is higher, and the risk of collision is increased without proper altitude information.

Ensuring that all aircraft are equipped with this technology enhances situational awareness for air traffic controllers and contributes to overall flight safety by facilitating more effective monitoring and managing of aircraft movements at higher altitudes.