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Aeronautical Information Manual (AIM), page 633

5/26/16
12/10/15

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 airspaces 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 nautical mile (NM)
radius, a circle with a 10NM radius that extends no
lower than 1,200 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 commu-
nications 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.
(See OUTER AREA.)
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
Pilot/Controller Glossary

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.
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.
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.
CONTROLLED TIME OF ARRIVAL- Arrival time
assigned during a Traffic Management Program. This
time may be modified due to adjustments or user
options.

CONTROLLER-
(See AIR TRAFFIC CONTROL SPECIALIST.)
CONTROLLER [ICAO]- A person authorized to
provide air traffic control services.
CONTROLLER PILOT DATA LINK
COMMUNICATIONS (CPDLC)- A two-way
digital communications system that conveys textual
air traffic control messages between controllers and
pilots using ground or satellite-based radio relay
stations.

PCG C-7

Page 633 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   632 -- Page 633 -- 634