Pilot/Controller Glossary Pilot/Controller Glossary  8/15/19 12/31/20  a.  Controlled airspace is a generic term that covers  Class A, Class B, Class C, Class D, and Class E  airspace.  b.  Controlled airspace is also that airspace within  which all aircraft operators are subject to certain pilot  qualifications, operating rules, and equipment  requirements in 14 CFR Part 91 (for specific  operating requirements, please refer to 14 CFR  Part 91). For IFR operations in any class of controlled  airspace, a pilot must file an IFR flight plan and  receive an appropriate ATC clearance. Each Class B,  Class C, and Class D airspace area designated for an  airport contains at least one primary airport around  which the airspace is designated (for specific  designations and descriptions of the airspace classes,  please refer to 14 CFR Part 71).  c.  Controlled airspace in the United States is  designated as follows:  1.  CLASS A- Generally, that airspace from  18,000 feet MSL up to and including FL 600,  including the airspace overlying the waters within 12  nautical miles of the coast of the 48 contiguous States  and Alaska. Unless otherwise authorized, all persons  must operate their aircraft under IFR.  2.  CLASS B- Generally, that airspace from the  surface to 10,000 feet MSL surrounding the nation's  busiest airports in terms of airport operations or  passenger enplanements. The configuration of each  Class B airspace area is individually tailored and  consists of a surface area and two or more layers  (some Class B airspace areas resemble upside-down  wedding cakes), and is designed to contain all  published instrument procedures once an aircraft  enters the airspace. An ATC clearance is required for  all aircraft to operate in the area, and all aircraft that  are so cleared receive separation services within the  airspace. The cloud clearance requirement for VFR  operations is “clear of clouds.”  3.  CLASS C- Generally, that 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 that have a certain  number of IFR operations or passenger enplane- ments. Although the configuration of each Class C  area is individually tailored, the airspace usually  consists of a surface area with a 5 NM radius, a circle  with a 10 NM radius that extends no lower than 1,200  CONTROLLED AIRSPACE [ICAO]- An airspace  of defined dimensions within which air traffic control  service is provided to IFR flights and to VFR flights  in accordance with the airspace classification.  Note: Controlled airspace is a generic term which  covers ATS airspace Classes A, B, C, D, and E.  5.  CLASS E- Generally, if the airspace is not  Class A, Class B, Class C, or Class D, and it is  controlled airspace, it is Class E airspace. Class E  airspace extends upward from either the surface or a  designated altitude to the overlying or adjacent  controlled airspace. When designated as a surface  area, the airspace will be configured to contain all  instrument procedures. Also in this class are Federal  airways, airspace beginning at either 700 or 1,200  feet AGL used to transition to/from the terminal or en  route environment, en route domestic, and offshore  airspace areas designated below 18,000 feet MSL.  Unless designated at a lower altitude, Class E  airspace begins at 14,500 MSL over the United  States, including that airspace overlying the waters  within 12 nautical miles of the coast of the 48  contiguous States and Alaska, up to, but not  including 18,000 feet MSL, and the airspace above  FL 600.  4.  CLASS D- Generally, that 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 will normally be designed to contain the  procedures. Arrival extensions for instrument  approach procedures may be Class D or Class E  airspace. Unless otherwise authorized, each person  must establish two-way radio communications with  the ATC facility providing air traffic services prior to  entering the airspace and thereafter maintain those  communications while in the airspace. No separation  services are provided to VFR aircraft.  (See OUTER AREA.)  feet up to 4,000 feet above the airport elevation, and  an outer area that is not charted. Each person must  establish two-way radio communications with the  ATC facility providing air traffic services prior to  entering the airspace and thereafter maintain those  communications while within the airspace. VFR  aircraft are only separated from IFR aircraft within  the airspace.  PCG C-7 