Approach says “N12345, standby.” May I enter?

AIM 3-2-4 says that if the controller responds with your aircraft call sign and “standby,” radio communications have been established and you may enter Class C. That is different from being told to remain outside.

What if they say “Aircraft calling Dulles approach control, standby”?

That reply does not use your aircraft identification. AIM 3-2-4 gives that sentence as the example of a reply that does not establish communications, and you may not enter. Stay outside and call again.

They used my call sign and said “remain outside the Class Charlie airspace and standby.”

Hearing your call sign is not permission to enter when the instruction is to remain outside. AIM 3-2-4 gives that phrase as an example. Stay outside until ATC provides the service.

Does an airplane without an electrical system get into Class C?

No. Section 91.215(b)(3) lets an aircraft that was not originally certificated with an engine-driven electrical system, and has not later been certificated with one, operate in the 30 NM Mode C veil only outside Class A, B, and C, and below the Class B or C ceiling or 10,000 feet MSL, whichever is lower. Relief from the transponder rule at and above 10,000 feet MSL for that aircraft is the exclusion in 91.215(b)(5), not (b)(3). Section 91.225(e) is the ADS-B rule: the same aircraft may operate without ADS-B Out in the Class E described in 91.225(d)(4), and in the Mode C veil only outside Class B and C and below that ceiling. Inside Class C, 91.130(d) still requires the 91.215 and 91.225 equipment unless ATC authorizes a deviation.

How do I ask for a deviation, and what about a satellite airport with no tower?

For an aircraft that is not equipped, 91.215(d)(3) and 91.225(g)(2) say the request must be made at least one hour before the operation. A request to fly with an inoperative transponder or inoperative ADS-B Out, to the destination or to a repair facility, may be made at any time. Departing a satellite airport without an operating control tower, 91.130(c)(2)(ii) says you establish and maintain communications with the ATC facility that has jurisdiction over the Class C as soon as practicable after departure.

Do you need two-way radio communication to enter Class C airspace?

Q: Do you need two-way radio communication to enter Class C airspace?

Yes, unless ATC authorizes otherwise. 14 CFR 91.130 requires two-way radio contact before Class C entry. AIM 3-2-4 explains when “standby” counts, plus Mode C (91.215) and ADS-B Out (91.225).

Yes, unless ATC has authorized otherwise. 14 CFR 91.130(c) says each person operating in Class C must establish two-way radio communications with the ATC facility providing air traffic services before entering, and must maintain those communications while inside. A reply that includes your call sign — including “[call sign] standby” — establishes communications. “Aircraft calling, standby,” without your call sign, does not. The airplane also needs the Mode C transponder in 91.215 and the ADS-B Out in 91.225, unless ATC authorizes a deviation.

Study aid, not legal advice. Regulations, the AIM, and handbook editions change. Check the current text and confirm anything that affects a flight or a checkride with your CFI.

What “established” means

Section 91.130(a) opens with “unless otherwise authorized by ATC.” If that authorization is not there, arrival or through-flight in paragraph (c)(1) has two parts: establish two-way communications with the facility providing air traffic services before you enter, then maintain them while you are in the airspace. Calling on the frequency is not enough. The AIM tells you when the reply counts.

AIM 3-2-4 says pilots should contact the facility on the publicized frequency and give position, altitude, radar beacon code, destination, and a request for Class C service, far enough out that you are not already inside when communications are established. Then:

If the controller answers with your call sign and “standby,” communications are established and you may enter.
If the controller answers the initial call without your aircraft identification, communications are not established and you may not enter. “Aircraft calling, standby” is the usual form of that reply.
If workload keeps the controller from providing Class C service, they will tell you to remain outside. The AIM’s example is “[call sign] remain outside the Class Charlie airspace and standby.” Your call sign is in that sentence, and you still stay out.

AIM 3-2-4 also describes a procedural Outer Area, normally 20 NM from the primary Class C airport. That outer area is not charted, participation there is voluntary, and it is not regulatory Class C. It is not a substitute for the entry rule once you reach the charted airspace. The charted Class C usually has a 5 NM radius core from the surface to 4,000 feet above the airport elevation, and a 10 NM radius shelf from no lower than 1,200 feet up to 4,000 feet above the airport elevation. Those altitudes are above the airport elevation, and the chart shows them in MSL. Individual areas are tailored, so the chart is the source for a particular airport.

Mode C and ADS-B Out

Section 91.130(d) says that, unless the ATC facility with jurisdiction authorizes otherwise, no person may operate in Class C unless the aircraft has the equipment specified in 91.215 and, after January 1, 2020, in 91.225.

Section 91.215(b)(1) applies in Class A, Class B, and Class C. Unless ATC authorizes or directs otherwise, the aircraft needs an operable transponder (Mode A 4096-code or Mode S, as the section specifies) and automatic pressure altitude reporting with Mode C capability, in 100-foot increments. “Mode C” on an oral is that altitude reporting, not a third squawk mode you select by hand.

Section 91.225(d)(1) lists Class B and Class C among the airspace where, after January 1, 2020 and unless ATC authorizes otherwise, the aircraft needs ADS-B Out meeting paragraph (b) of that section and § 91.227. Below 18,000 feet MSL, paragraph (b) allows either 1090ES or UAT equipment that meets the TSO performance the rule names.

AIM 3-2-4 states the same equipment pair in plain language: a two-way radio, and unless ATC authorizes otherwise, an operable transponder with automatic altitude reporting and operable ADS-B Out.

Departures and the 200-knot limit

From the primary airport, or a satellite airport with an operating control tower, 91.130(c)(2)(i) requires two-way communications with the tower, and thereafter as ATC instructs while you are in the Class C. From a satellite airport without a tower, you establish communications with the facility that has jurisdiction as soon as practicable after you depart.

Section 91.117(b) is a separate limit examiners attach to this airspace: unless ATC authorizes or requires otherwise, at or below 2,500 feet above the surface and within 4 nautical miles of the primary airport of a Class C or Class D area, indicated airspeed may not be more than 200 knots (230 mph). That paragraph does not apply inside Class B; those operations follow 91.117(a). If the minimum safe airspeed for the operation is higher than the limit, 91.117(d) allows that minimum speed.

Class C is also an oral topic under ACS Area I, Task E (National Airspace System) and Area III (communications). The 30-day oral checklist puts airspace on day 5 and radio calls on day 8.

Common examiner follow-ups

Approach says “N12345, standby.” May I enter?: AIM 3-2-4 says that if the controller responds with your aircraft call sign and “standby,” radio communications have been established and you may enter Class C. That is different from being told to remain outside.
What if they say “Aircraft calling Dulles approach control, standby”?: That reply does not use your aircraft identification. AIM 3-2-4 gives that sentence as the example of a reply that does not establish communications, and you may not enter. Stay outside and call again.
They used my call sign and said “remain outside the Class Charlie airspace and standby.”: Hearing your call sign is not permission to enter when the instruction is to remain outside. AIM 3-2-4 gives that phrase as an example. Stay outside until ATC provides the service.
Does an airplane without an electrical system get into Class C?: No. Section 91.215(b)(3) lets an aircraft that was not originally certificated with an engine-driven electrical system, and has not later been certificated with one, operate in the 30 NM Mode C veil only outside Class A, B, and C, and below the Class B or C ceiling or 10,000 feet MSL, whichever is lower. Relief from the transponder rule at and above 10,000 feet MSL for that aircraft is the exclusion in 91.215(b)(5), not (b)(3). Section 91.225(e) is the ADS-B rule: the same aircraft may operate without ADS-B Out in the Class E described in 91.225(d)(4), and in the Mode C veil only outside Class B and C and below that ceiling. Inside Class C, 91.130(d) still requires the 91.215 and 91.225 equipment unless ATC authorizes a deviation.
How do I ask for a deviation, and what about a satellite airport with no tower?: For an aircraft that is not equipped, 91.215(d)(3) and 91.225(g)(2) say the request must be made at least one hour before the operation. A request to fly with an inoperative transponder or inoperative ADS-B Out, to the destination or to a repair facility, may be made at any time. Departing a satellite airport without an operating control tower, 91.130(c)(2)(ii) says you establish and maintain communications with the ATC facility that has jurisdiction over the Class C as soon as practicable after departure.

Sources

Checked against the eCFR, the AIM, and FAA-H-8083-25C on October 29, 2026. The eCFR is updated continuously; the link opens the current section.