What is the key radio communication rule for entering Class C airspace — when is communication 'established'?

3-2-4. Class C Airspace
a. Definition. 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 enplanements. Although the configuration of each
Class C airspace area is individually tailored, the airspace usually consists of a 5 NM radius core surface area
that extends from the surface up to 4,000 feet above the airport elevation, and a 10 NM radius shelf area that
extends no lower than 1,200 feet up to 4,000 feet above the airport elevation.
b. Charts. Class C airspace is charted on Sectional Charts, IFR En Route Low Altitude, and Terminal Area
Charts where appropriate.
c. Operating Rules and Pilot/Equipment Requirements:
1. Pilot Certification. No specific certification required.
2. Equipment.
(a) Two-way radio; and
(b) Unless otherwise authorized by ATC, an operable radar beacon transponder with automatic altitude
reporting capability and operable ADS-B Out equipment.
NOTE-
See paragraph 4 -1-20, Transponder and ADS -B Out Operation, subparagraph f for Mode C transponder/ ADS -B
requirements for operating above Class C airspace.
3. Arrival or Through Flight Entry Requirements. Two-way radio communication must be established
with the ATC facility providing ATC services prior to entry and thereafter maintain those communications while
in Class C airspace. Pilots of arriving aircraft should contact the Class C airspace ATC facility on the publicized
frequency and give their position, altitude, radar beacon code, destination, and request Class C service. Radio
contact should be initiated far enough from the Class C airspace boundary to preclude entering Class C airspace
before two-way radio communications are established.
NOTE-
1. If the controller responds to a radio call with, "(aircraft callsign) standby," radio communications have been established
and the pilot can enter the Class C airspace.
2. If workload or traffic conditions prevent immediate provision of Class C services, the controller will inform the pilot to
remain outside the Class C airspace until conditions permit the services to be provided.
3. It is important to understand that if the controller responds to the initial radio call without using the aircraft identification,
radio communications have not been established and the pilot may not enter the Class C airspace.
4. Class C airspace areas have a procedural Outer Area. Normally this area is 20 NM from the primary Class C airspace
airport. Its vertical limit extends from the lower limits of radio/radar coverage up to the ceiling of the approach control' s
delegated airspace, excluding the Class C airspace itself, and other airspace as appropriate. (This outer area is not charted.)
5. Pilots approaching an airport with Class C service should be aware that if they descend below the base altitude of the
5 to 10 mile shelf during an instrument or visual approach, they may encounter non-transponder/non-ADS-B VFR aircraft.
EXAMPLE-
1. [Aircraft callsign] "remain outside the Class Charlie airspace and standby."
2. "Aircraft calling Dulles approach control, standby."
4. Departures from:
Controlled Airspace 3-2-5

AIM 2/20/25
(a) A primary or satellite airport with an operating control tower. Two-way radio communications must
be established and maintained with the control tower, and thereafter as instructed by ATC while operating in
Class C airspace.
(b) A satellite airport without an operating control tower. Two-way radio communications must be
established as soon as practicable after departing with the ATC facility having jurisdiction over the Class C
airspace.
5. Aircraft Speed. Unless otherwise authorized or required by ATC, no person may operate an aircraft at
or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C airspace area
at an indicated airspeed of more than 200 knots (230 mph).
d. Air Traffic Services. When two-way radio communications and radar contact are established, all VFR
aircraft are:
1. Sequenced to the primary airport.
2. Provided Class C services within the Class C airspace and the outer area.
3. Provided basic radar services beyond the outer area on a workload permitting basis. This can be
terminated by the controller if workload dictates.
e. Aircraft Separation. Separation is provided within the Class C airspace and the outer area after two-way
radio communications and radar contact are established. VFR aircraft are separated from IFR aircraft within the
Class C airspace by any of the following:
1. Visual separation.
2. 500 feet vertical separation.
3. Target resolution.
4. Wake turbulence separation will be provided to all aircraft operating:
(a) Behind and less than 1,000 feet below super or heavy aircraft,
(b) To small aircraft operating behind and less than 500 feet below B757 aircraft, and
(c) To small aircraft following a large aircraft on final approach.
NOTE-
1. Separation and sequencing of VFR aircraft will be suspended in the event of a radar outage as this service is dependent
on radar. The pilot will be advised that the service is not available and issued wind, runway information and the time or place
to contact the tower.
2. Pilot participation is voluntary within the outer area and can be discontinued, within the outer area, at the pilot' s request.
Class C services will be provided in the outer area unless the pilot requests termination of the service.
3. Some facilities provide Class C services only during published hours. At other times, terminal IFR radar service will be
provided. It is important to note that the communications and transponder/ADS-B requirements are dependent on the class
of airspace established outside of the published hours.
f. Secondary Airports
1. In some locations Class C airspace may overlie the Class D surface area of a secondary airport. In order
to allow that control tower to provide service to aircraft, portions of the overlapping Class C airspace may be
procedurally excluded when the secondary airport tower is in operation. Aircraft operating in these procedurally
excluded areas will only be provided airport traffic control services when in communication with the secondary
airport tower.
2. Aircraft proceeding inbound to a satellite airport will be terminated at a sufficient distance to allow time
to change to the appropriate tower or advisory frequency. Class C services to these aircraft will be discontinued
when the aircraft is instructed to contact the tower or change to advisory frequency.
3-2-6 Controlled Airspace

2/20/25 AIM
3. Aircraft  departing secondary controlled airports will not receive Class C services until they have been
radar identified and two-way communications have been established with the Class C airspace facility.
4. This program is not to be interpreted as relieving pilots of their responsibilities to see and avoid other
traffic operating in basic VFR weather conditions, to adjust their operations and flight path as necessary to
preclude serious wake encounters, to maintain appropriate terrain and obstruction clearance or to remain in
weather conditions equal to or better than the minimums required by 14 CFR section 91.155. Approach control
should be advised and a revised clearance or instruction obtained when compliance with an assigned route,
heading and/or altitude is likely to compromise pilot responsibility with respect to terrain and obstruction
clearance, vortex exposure, and weather minimums.
g. Class C Airspace Areas by State. These states currently have designated Class C airspace areas that are
depicted on sectional charts. Pilots should consult current sectional charts and NOTAMs for the latest
information on services available. Pilots should be aware that some Class C airspace underlies or is adjacent to
Class B airspace. (See TBL 3-2-1.)
TBL 3-2-1
Class C Airspace Areas by State
State/City Airport
ALABAMA
Birmingham .........
Huntsville ...........
Mobile ..............
Birmingham-Shuttlesworth
International
International-Carl T Jones Fld
Regional
ALASKA
Anchorage ........... Ted Stevens International
ARIZONA
Davis-Monthan .......
Tucson ..............
AFB
International
ARKANSAS
Fayetteville (Springdale) Northwest Arkansas Regional
Little Rock .......... Adams Field
CALIFORNIA
Beale ...............
Burbank ............
Fresno ..............
Monterey ............
Oakland .............
Ontario .............
Riverside ............
Sacramento ..........
San Jose ............
Santa Ana ...........
Santa Barbara ........
AFB
Bob Hope
Yosemite International
Peninsula
Metropolitan Oakland
International
International
March AFB
International
Norman Y . Mineta International
John Wayne/Orange County
Municipal
COLORADO
Colorado Springs ..... Municipal
CONNECTICUT
Windsor Locks ....... Bradley International
FLORIDA
Daytona Beach .......
Fort Lauderdale .......
Fort Myers ..........
Jacksonville ..........
Orlando .............
International
Hollywood International
SW Florida Regional
International
Sanford International
State/City Airport
Palm Beach ..........
Pensacola ...........
Pensacola ...........
Sarasota .............
Tallahassee ..........
Whiting .............
International
NAS
International
Bradenton International
Regional
NAS
GEORGIA
Savannah ............ Hilton Head International
HAWAII
Kahului ............. Kahului
IDAHO
Boise ............... Air Terminal
ILLINOIS
Champaign .......... Urbana U of Illinois-Willard
Chicago .............
Moline ..............
Peoria ..............
Springfield ..........
Midway International
Quad City International
Greater Peoria Regional
Abraham Lincoln Capital
INDIANA
Evansville ...........
Fort Wayne ..........
Indianapolis ..........
South Bend ..........
Regional
International
International
Regional
IOWA
Cedar Rapids .........
Des Moines ..........
The Eastern Iowa
International
KANSAS
Wichita ............. Mid-Continent
KENTUCKY
Lexington ...........
Louisville ...........
Blue Grass
International-Standiford Field
LOUISIANA
Baton Rouge .........
Lafayette ............
Shreveport ...........
Metropolitan, Ryan Field
Regional
Barksdale AFB
Controlled Airspace 3-2-7

 AIM 2/20/25
State/City Airport
Shreveport ........... Regional
MAINE
Bangor .............
Portland .............
International
International Jetport
MICHIGAN
Flint ................
Grand Rapids ........
Lansing .............
Bishop International
Gerald R. Ford International
Capital City
MISSISSIPPI
Columbus ...........
Jackson .............
AFB
Jackson-Evers International
MISSOURI
Springfield .......... Springfield-Branson National
MONTANA
Billings ............. Logan International
NEBRASKA
Lincoln .............
Omaha ..............
Offutt ...............
Lincoln
Eppley Airfield
AFB
NEV ADA
Reno ............... Reno/Tahoe International
NEW HAMPSHIRE
Manchester .......... Manchester
NEW JERSEY
Atlantic City ......... International
NEW MEXICO
Albuquerque ......... International Sunport
NEW YORK
Albany .............
Buffalo .............
Islip ................
Rochester ...........
Syracuse ............
International
Niagara International
Long Island MacArthur
Greater Rochester International
Hancock International
NORTH CAROLINA
Asheville ...........
Fayetteville ..........
Greensboro ..........
Pope ...............
Raleigh .............
Regional
Regional/Grannis Field
Piedmont Triad International
AFB
Raleigh-Durham International
OHIO
Akron ..............
Columbus ...........
Dayton .............
Toledo ..............
Akron-Canton Regional
Port Columbus International
James M. Cox International
Express
OKLAHOMA
Oklahoma City .......
Tinker ..............
Tulsa ...............
Will Rogers World
AFB
International
OREGON
Portland ............. International
State/City Airport
PENNSYLV ANIA
Allentown ........... Lehigh Valley International
PUERTO RICO
San Juan ............ Luis Munoz Marin International
RHODE ISLAND
Providence .......... Theodore Francis Green State
SOUTH CAROLINA
Charleston ...........
Columbia ............
Greer ...............
Myrtle Beach ........
Shaw ...............
AFB/International
Metropolitan
Greenville-Spartanburg
International
Myrtle Beach International
AFB
TENNESSEE
Chattanooga .........
Knoxville ...........
Nashville ............
Lovell Field
McGhee Tyson
International
TEXAS
Abilene .............
Amarillo ............
Austin ..............
Corpus Christi ........
Dyess ..............
El Paso .............
Harlingen ...........
Laughlin ............
Lubbock ............
Midland .............
San Antonio .........
Regional
Rick Husband International
Austin-Bergstrom International
International
AFB
International
Valley International
AFB
Preston Smith International
International
International
VERMONT
Burlington ........... International
VIRGIN ISLANDS
St. Thomas .......... Charlotte Amalie Cyril E. King
VIRGINIA
Richmond ...........
Norfolk .............
International
International
Roanoke ............ Regional/Woodrum Field
WASHINGTON
Point Roberts ........
Spokane ............
Spokane ............
Whidbey Island .......
Vancouver International
Fairchild AFB
International
NAS, Ault Field
WEST VIRGINIA
Charleston ........... Yeager
WISCONSIN
Green Bay ...........
Madison ............
Milwaukee ..........
Austin Straubel International
Dane County Regional-Traux
Field
General Mitchell International