At what altitude is an operating mode C transponder required while flying over class B airspace?

An operating mode C transponder is required when flying at or above 10,000 feet MSL (Mean Sea Level) in Class B airspace to enhance safety and situational awareness. This designation allows air traffic control and other aircraft in the vicinity to accurately track and communicate with transponder-equipped aircraft. The altitude requirement is set to provide better radar coverage and improve the ability to separate traffic, particularly in busy airspace.

Flying above 10,000 feet, especially in proximity to Class B airspace, presents higher traffic density and potential conflict, making the transponder a crucial safety tool. Even when operating within the confines of Class B airspace, any altitude above 10,000 feet necessitates this equipment to help maintain safe operations among various types of aircraft.