What is classified as uncontrolled airspace?

Uncontrolled airspace is defined as airspace where air traffic control does not provide air traffic services to pilots. Class G airspace fits this definition perfectly. It comprises the lowest levels of airspace, generally used for visual flight rules (VFR) operations. In this airspace, pilots operate without air traffic control guidance and can fly freely as long as they adhere to the regulations and visibility requirements pertaining to VFR flights.

In contrast, Class A, Class D, and Class C airspaces are controlled. Class A airspace extends from 18,000 feet mean sea level to 60,000 feet and requires pilots to operate under instrument flight rules, with air traffic control managing all flights. Class D airspace surrounds airports with an operating control tower and involves ATC communication for entry and operations, while Class C airspace surrounds busier airports and also requires communication with air traffic control.