Aircraft must be equipped with an operable transponder with Mode C altitude reporting in which airspace?

Aircraft must be equipped with an operable transponder with Mode C altitude reporting in which airspace?

• A. Class A airspace only
• B. Class A, B, and C airspace
• C. All airspace without exception
• D. Class B and C airspace

Answer: (B)

Mode C altitude reporting helps ATC see both position and vertical aircraft separation on radar. This is required in airspace where ATC provides radar services and enforces separation, which includes Class A, Class B, and Class C. In Class A, all operations are under ATC control and require an operable transponder with altitude reporting. In Class B and Class C, the high traffic levels and radar vectors likewise rely on altitude data to manage separation safely. Other airspace such as Class D, E, or G does not carry the blanket requirement for Mode C, so the combination that needs this equipment is Class A, B, and C.

Mode C altitude reporting helps ATC see both position and vertical aircraft separation on radar. This is required in airspace where ATC provides radar services and enforces separation, which includes Class A, Class B, and Class C. In Class A, all operations are under ATC control and require an operable transponder with altitude reporting. In Class B and Class C, the high traffic levels and radar vectors likewise rely on altitude data to manage separation safely. Other airspace such as Class D, E, or G does not carry the blanket requirement for Mode C, so the combination that needs this equipment is Class A, B, and C.