Under Visual Flight Rules (VFR) in Visual Meteorological Conditions (VMC), the only type of controlled airspace where you are generally not required to establish radio communication with Air Traffic Control (ATC) is Class E airspace. While Class E is considered controlled airspace, it is primarily controlled for the benefit of IFR (Instrument Flight Rules) traffic. VFR pilots can fly through Class E without a specific clearance or radio contact, provided they maintain the required VMC weather minima (visibility and distance from clouds) and have their transponder on if required by the specific altitude or location (such as being within a Mode C veil). In all other classes of controlled airspace in the U.S.—specifically Class A, B, C, and D—VFR pilots must either establish two-way radio communication or receive an explicit ATC clearance before entry. Class G is uncontrolled airspace, so communication is also not required there, but Class E remains the unique "hybrid" where control is active for IFR but not mandatory for VFR pilots under standard daytime conditions.