Chapter 2: Airspace Classification, Operating Requirements, and Flight Restrictions Class C Airspace Class D Airspace Class E Airspace Uncontrolled Airspace  Class G Airspace Special Use Airspace Remote Pilot – Small Unmanned Aircraft Systems Study Guide  6  Special use airspace or special area of operation (SAO) is the designation for airspace in which certain  activities must be confined, or where limitations may be imposed on aircraft operations that are not  part of those activities. Certain special use airspace areas can create limitations on the mixed use of  airspace. The special use airspace depicted on instrument charts includes the area name or number,  Uncontrolled airspace or Class G airspace is the portion of the airspace that has not been designated  as Class A, B, C, D, or E. It is therefore designated uncontrolled airspace. Class G airspace extends  from the surface to the base of the overlying Class E airspace. A remote pilot will not need ATC  authorization to operate in Class G airspace.  In most cases, a remote pilot will not need ATC authorization to operate in Class E airspace.  Federal Airways, which are shown as blue lines on a sectional chart, are usually found within Class E  airspace. Federal Airways start at 1,200’ AGL and go up to, but, not including 18,000’ MSL. Sectional and other charts depict all locations of Class E airspace with bases below 14,500 feet MSL.  In areas where charts do not depict a class E base, class E begins at 14,500 feet MSL. In most areas,  the Class E airspace base is 1,200 feet above ground level (AGL). In many other areas, the Class E  airspace base is either the surface or 700 feet AGL. Some Class E airspace begins at an MSL altitude  depicted on the charts, instead of an AGL altitude. Class E airspace typically extends up to, but not  including, 18,000 feet MSL (the lower limit of Class A airspace). All airspace above FL 600 is Class E  airspace. Class E airspace is the controlled airspace not classified as Class A, B, C, or D airspace. A large  amount of the airspace over the United States is designated as Class E airspace. This provides  sufficient airspace for the safe control and separation of aircraft during IFR operations. Chapter 3 of  the  Aeronautical Information Manual (AIM) explains the various types of Class E airspace.  Class D airspace is generally airspace from the surface to 2,500 feet above the airport elevation  (charted in MSL) surrounding those airports that have an operational control tower. The  configuration of each Class D airspace area is individually tailored and, when instrument procedures  are published, the airspace is normally designed to contain the procedures. Arrival extensions for  instrument approach procedures (IAPs) may be Class D or Class E airspace. A remote pilot must  receive ATC authorization before operating in Class D airspace.  Class C airspace is generally airspace from the surface to 4,000 feet above the airport elevation  (charted in MSL) surrounding those airports that have an operational control tower, are serviced by  a radar approach control, and have a certain number of instrument flight rules (IFR) operations or  passenger enplanements. Although the configuration of each Class C area is individually tailored, the  airspace usually consists of a surface area with a five nautical mile (NM) radius, an outer circle with a  ten NM radius that extends from 1,200 feet to 4,000 feet above the airport elevation. A remote pilot  must receive authorization before operating in Class C airspace. 