What characterizes Class E airspace?

Class E airspace is indeed characterized as controlled airspace that is not classified as A, B, C, or D. This type of airspace is designed to provide IFR (Instrument Flight Rules) and VFR (Visual Flight Rules) operations an area to operate safely with separation from other aircraft. Class E airspace generally starts at either the surface or a designated altitude and extends upwards to the base of the overlying controlled airspace, which can include Class A airspace above 18,000 feet MSL.

Class E is often used for en route operations and can also be found in specific areas where additional airspace is required for safety or efficiency, such as around airports where IFR operations are expected. Its flexible nature allows for a variety of operational needs, serving both commercial and private aviation interests.

The other choices don't correctly describe Class E airspace. For example, it is not considered uncontrolled airspace (that's more accurately described as Class G airspace), nor does it exclusively pertain to military operations. Additionally, Class E airspace does not solely exist above 18,000 feet MSL, as it can also exist at lower altitudes. Hence, the correct understanding of Class E is critical for pilots navigating within this type of