What is the normal radius of the procedural Outer Area of Class C airspace?

The normal radius of the procedural Outer Area of Class C airspace is set at 20 nautical miles. This distance is defined by regulations to help manage traffic safely around airports with a significant volume of aircraft and to facilitate communication and navigation for pilots.

The Class C airspace structure commonly includes a core area, which typically extends from the surface up to 4,000 feet above the airport elevation, and then a surrounding Outer Area that provides a buffer zone for incoming and outgoing aircraft. Having a 20 nautical mile radius allows air traffic control to provide radar service and maintain safe separation between aircraft as they approach and depart from busy airports, while also allowing them to manage traffic efficiently in that zone.

In contrast, the other distances listed are not designated as standard for Class C airspace and would not comply with the established procedures and dimensions set forth by the FAA regulations governing air traffic management.