What is the minimum altitude MSL that requires an operable coded transponder?

The minimum altitude above mean sea level (MSL) at which an operable coded transponder is required is 10,000 feet MSL. This requirement is primarily in place to ensure that aircraft operating at higher altitudes can be effectively tracked by air traffic control, especially in busy airspace. The transponder enhances radar detection capabilities, allowing for safer separation of aircraft and improving situational awareness for both pilots and controllers.

When operating above this altitude, a functioning transponder is critical for maintaining safety in the skies since it provides vital information about an aircraft's altitude and position. Below 10,000 feet, while a transponder is generally recommended, it is not mandated under the same circumstances. This regulatory framework is intended to balance safety needs with operational flexibility in lower altitude operations.