What airspace covers areas outside Classes B, C, and D?

The correct answer is Class E. This class of airspace is designed to accommodate various types of aircraft operations outside the strict requirements of Classes B, C, and D while still allowing controlled airspace for IFR (Instrument Flight Rules) operations. Class E airspace typically extends from either the surface or a specified altitude up to the base of Class A airspace, providing a transition zone for aircraft flying under IFR or VFR (Visual Flight Rules).

Class E is crucial as it allows for air traffic control services and supports operations in areas that do not require the more stringent regulations applied in Class B, C, and D airspaces. It commonly exists in areas where there is a need for controlled airspace without the complexity of larger airports and more significant traffic.

In contrast, other classes such as Class A, which is designed for high-altitude operations generally above 18,000 feet, are not applicable to areas outside the aforementioned classes. Class G represents uncontrolled airspace, where air traffic control services are not provided and would not cover areas classified under controlled airspace. Class D relates specifically to controlled airspace surrounding airports with operating control towers, which does not encompass the broader areas managed under Class E.