Definitions are from the
Pilot/Controller Glossary (7110.65H) and are listed in alphabetical order.
Class G - (uncontrolled airspace)
That airspace not designated as Class A, B, C, D, or E.
Controlled Airspace - An airspace of defined dimensions within
which air traff ic control service is provided to I FR flights and to VFR
flights in accordance with the airspace classification.
Note 1 - Controlled airspace is a generic term that covers Class A,
Class B, Class C, Class D, and Class E airspace.
Note 2 - Controlled airspace is also that airspace within which all
aircraft operators are subject to certain pilot qualifications, operating
rules, and equipment requirements in FAR Part 91 (for specific operating
requirements, please refer to FAR 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 FAR Part 71).
Controlled airspace in the United States is designated as follows:
Class A - Generally, that airspace from 18,000 feet MSL up to and
including FL600, 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.
Class B - Generally, that airspace from the surface to 10,000 feet
MSL surrounding the nation's busiest airports in terms of IFR 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."
Class C - Generally that airspace from the surface to 4,000 feet
above the airport elevation (charted in MSQ 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
enplanements. Although the configuration of each Class C airspace area is
individually tailored, the airspace usually consists of a surface area
with a 5NM radius, and an outer circle with a 1 ONM radius that extends
from 1,200 feet to 4,000 feet above the airport elevation. 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.
Class D - Generally, that airspace from the surface to 2,500 feet
above the airport elevation (charted in MSQ 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.
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 AGIL used to transition to/from the
terminal or enroute environment, enroute 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. Class E airspace does
not include the airspace 18,000 MSL or above.
Service - A generic term that designates functions or assistance
available from or rendered by air traffic control. For example, Class C
service would denote the ATC services provided within a Class C airspace
Special VFR Operations - Aircraft operating in accordance with
clearances in Class B, C, D, or E surface areas in weather conditions less
than the basic VFR weather minimum. Such operations must be requested by
the pilot and approved by ATC.
Surface Area - The airspace contained by the lateral boundary of
the Class B, C, D, or E airspace designated for an airport that begins at
the surface and extends upward.
Terminal VFR Radar Service - A national program instituted to
extend the terminal radar services provided to instrument flight rules (IFR)
aircraft to visual flight rules (VFR) aircraft. The program is divided
into four types of service referred to as basic radar service, terminal
radar service area (TRSA) service, Class B service and Class C service.
The type of service provided at a particular location is contained in the
1. Basic Radar Service: These services are provided for VFR
aircraft by all commissioned terminal radar facilities. Basic radar
service includes safety alerts, traffic advisories, limited radar
vectoring when requested by the pilot, and sequencing at locations where
procedures have been established for this purpose and/or when covered by
a letter of agreement. The purpose of this service is to adjust the flow
of arriving lFR and VFR aircraft into the traffic pattern in a safe and
orderly manner and to provide traffic advisories to departing VFR
2. TRSA Service: This service provides, in addition to basic
radar service, sequencing of all lFR and participating VFR aircraft to
the primary airport and separation between all participating VFR
aircraft. The purpose of this service is to provide separation between
all participating VFR aircraft and all IFR aircraft operating within the
area defined as a TRSA.
3. Class C Service: This service provides, in addition to basic
radar service, approved separation between lFR and VFR aircraft, and
sequencing of VFR arrivals to the primary airport.
4. Class B Service: This service provides, in addition to basic
radar service, approved separation of aircraft based on IFR, VFR, and/or
weight, and sequencing of VFR arrivals to the primary airport(s).
* Authorized by an ATC clearance and conducted within the
lateral boundaries of the surface area.
** Flight visibility and cloud clearance requirements differ for operations
below 1,200 feet AGL, above 1,200 feet AGL but below 10,000 feet MSL, above
10,000 feet MSL, day, night, or student pilot. See FARs 61.89 and 91.155 for
NOTE: IFR operations in controlled airspace require filing an IFR flight
plan and an appropriate ATC clearance.
U.S. Airspace Classes
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