Which type of flight is generally allowed in Class G airspace without ATC clearance?

Class G airspace, also known as uncontrolled airspace, is where pilots can operate without the need for Air Traffic Control (ATC) clearance. In this type of airspace, Visual Flight Rules (VFR) flights are permitted, allowing pilots to navigate and operate based on visual references outside the cockpit. This freedom is afforded to pilots operating under VFR as they maintain the responsibility for their own separation from other aircraft and obstacles, which is the cornerstone of flying in uncontrolled airspace.

Instrument Flight Rules (IFR) flights, on the other hand, require communication with ATC for clearances, routing, and separation from other traffic. Commercial flights typically follow either VFR or IFR depending on the flight plan, but in Class G airspace, only VFR operations do not require ATC clearance. Hence, VFR flight is the only type of flight that is generally allowed in Class G airspace without the necessity of obtaining prior clearance from ATC.