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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.