What are the vertical limits of Class G airspace?

Class G airspace is the unregulated airspace that exists below the controlled airspace, and its vertical limits are defined by the surface up to the overlying controlled airspace. This means that Class G airspace begins at ground level or the surface and extends upward until it meets Class E (or other controlled airspace) boundaries.

The correct answer accurately reflects this definition that Class G airspace continues to exist wherever there is no controlled airspace above it, allowing for operations without the strict requirements that govern higher airspaces. This unregulated airspace provides pilots the flexibility to operate under visual flight rules (VFR) and can vary in altitude depending on the specific airspace structure above it.

In practice, Class G can start from ground level and continues indefinitely upward until it transitions to controlled airspace, which can range from 1,200 feet AGL to any altitude, depending on the airspace configuration.