Which airspace classification requires two-way radio communication with ATC?

The requirement for two-way radio communication with Air Traffic Control (ATC) is a key factor for safety and efficiency in managing air traffic. In Class B, Class C, and Class D airspaces, communication with ATC is necessary to ensure that aircraft can operate safely within controlled environments where other aircraft are also present and where separation of traffic needs to be actively managed.

In Class B airspace, which typically surrounds the busiest airports, communication is essential for maintaining safe distances between multiple aircraft and for coordinating arrivals and departures. Similarly, Class C airspace, which often includes airports with a significant amount of airport traffic but less than Class B, also necessitates two-way communication to ensure safe operations. Class D airspace, often encompassing smaller airports with control towers, requires two-way communication to ensure that departing and arriving flights can be managed effectively and safely.

The other classifications mentioned either do not require two-way communication or apply under different conditions. For example, Class E airspace requires communication under certain conditions, mainly during Instrument Flight Rules (IFR) operations, but not universally for all flights. Class G airspace is uncontrolled airspace, meaning that pilots do not need to communicate with ATC unless they choose to do so.