Class G (uncontrolled) airspace is that portion of airspace not designated as Class A, B, C, D, or E (or Class F, where applicable).

Uncontrolled airspace or Class G airspace is the portion of the airspace that has not been designated as Class A, B, C, D, or E (or Class F, for countries which use that airspace class). It is therefore designated uncontrolled airspace. Class G extends from the surface to the base of the overlying Class E airspace. Although ATC has no authority or responsibility to control air traffic, pilots should remember there are visual flight rules (VFR) minimums which apply to Class G airspace.