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AIM

10/12/17

3

−2−10

Controlled Airspace

NOTE

When a Class C or Class D surface area is not in effect
continuously (for example, where a control tower only
operates part-time), the surface area airspace will change
to either a Class E surface area or Class G airspace. In
such cases, the “Airspace” entry for the airport in the
Chart Supplement U.S. will state “other times Class E” or
“other times Class G.” When a part-time surface area
changes to Class E airspace, the Class E arrival extensions
will remain in effect as Class E airspace. If a part–time
Class C, Class D, or Class E surface area becomes Class
G airspace, the arrival extensions will change to Class G
at the same time.

3. Airspace used for transition.

Class E

airspace areas may be designated for transitioning
aircraft to/from the terminal or en route environment.

(a)

Class E transition areas extend upward

from either 700 feet AGL (shown as magenta vignette
on sectional charts) or 1,200 feet AGL (blue vignette)
and are designated for airports with an approved
instrument procedure.

(b)

The 700-foot/1200-foot AGL Class E

airspace transition areas remain in effect continu-
ously, regardless of airport operating hours or surface
area status.

NOTE

Do not confuse the 700-foot and 1200-foot Class E
transition areas with surface areas or surface area
extensions.

4. En Route Domestic Areas.

There are

Class E airspace areas that extend upward from a
specified altitude and are en route domestic airspace
areas that provide controlled airspace in those areas
where there is a requirement to provide IFR en route

ATC services but the Federal airway system is
inadequate.

5. Federal Airways and Low-Altitude RNAV

Routes. 

Federal airways and low-altitude RNAV

routes are Class E airspace areas and, unless
otherwise specified, extend upward from 1,200 feet
AGL to, but not including,18,000 feet MSL.

(a)

Federal airways consist of Low/Medium

Frequency (L/MF) airways (colored Federal airways)
and VOR Federal airways.

(1)

L/MF airways are based on non

−direc-

tional beacons (NDB) and are identified as green, red,
amber, or blue.

(2)

VOR Federal airways are based on

VOR/VORTAC facilities and are identified by a “V”
prefix.

(b)

Low-altitude RNAV routes consist of

T-routes and helicopter RNAV routes (TK-routes).

NOTE

See AIM Paragraph 5-3-4, Airways and Route Systems, for
more details and charting information.

6. Offshore Airspace Areas.

There are

Class E airspace areas that extend upward from a
specified altitude to, but not including, 18,000 feet
MSL and are designated as offshore airspace areas.
These areas provide controlled airspace beyond
12 miles from the coast of the U.S. in those areas
where there is a requirement to provide IFR en route
ATC services and within which the U.S. is applying
domestic procedures.

f. Separation for VFR Aircraft.

No separation

services are provided to VFR aircraft.