In which airspaces is a Mode C Transponder required?

A Mode C transponder is required in Class A, B, and C airspace primarily to enhance situational awareness and improve safety for all aircraft operating in these controlled environments.

In Class A airspace, which is airspace from 18,000 feet MSL up to 60,000 feet MSL, the requirement for a Mode C transponder is crucial because this airspace is heavily trafficked, requiring continuous air traffic control services and the ability to monitor aircraft positions accurately.

In Class B airspace, surrounding the busiest airports, the Mode C transponder helps ensure that Air Traffic Control (ATC) can segregate and manage traffic efficiently. Aircraft must be equipped with a transponder to both enter and operate within this airspace, thus aiding in collision prevention.

In Class C airspace, which generally surrounds airports with a moderate volume of traffic, the requirement for a Mode C transponder allows ATC to maintain an accurate picture of the traffic situation, which is essential for sequencing arrivals and departures.

While there are requirements for transponder use in other airspace classes, such as at certain altitudes below 10,000 feet MSL or in certain circumstances, the specification for a Mode C transponder being mandatory in Class A,