Understanding U.S. Airspace Classes (B, C, D, E, G)

U.S. airspace is divided into classes that determine what authorization, if any, a drone pilot needs before flying.

Key takeaways

For both Part 107 pilots and recreational flyers, prior air traffic control (ATC) authorization is required in Class B, Class C, Class D, and within the lateral boundaries of a Class E surface area designated for an airport.
Class G is uncontrolled airspace. No ATC authorization is needed there, but the 400-foot limit, visual line of sight, and every other rule still apply.
Class A starts at 18,000 feet MSL, far above anything a small drone is allowed to reach.
Class D can be part-time, and Class E comes in several forms, so a quick glance at a map is not enough. Check a current chart or an FAA-approved app for your exact spot.
Authorization is only one layer. Temporary flight restrictions and NOTAMs apply on top of the airspace class.

The rule behind the classes

The key regulation for commercial and work-related flights is 14 CFR 107.41. It says no one may operate a small unmanned aircraft in Class B, Class C, or Class D airspace, or within the lateral boundaries of the surface area of Class E airspace designated for an airport, without prior authorization from ATC (eCFR, 14 CFR 107.41). Recreational flyers operating under the Exception for Limited Recreational Operations (49 U.S.C. 44809) face the same condition. The FAA's recreational pages describe the same two ways to obtain authorization: LAANC and FAA DroneZone.

The classes are a way of describing who is talking to whom. In controlled airspace, air traffic controllers are actively communicating with, directing, and separating air traffic. Asking for authorization is how a drone pilot gets into that picture before the flight rather than after a conflict.

Quick reference table

Class	Typical vertical extent	What it surrounds	Drone authorization
A	18,000 ft MSL up to FL 600	High-altitude airspace across the country	Not relevant to normal small-drone flight
B	Surface to 10,000 ft MSL (layered)	The busiest airports	Required
C	Surface to 4,000 ft above airport elevation	Towered airports with radar approach control	Required
D	Surface to 2,500 ft above airport elevation	Airports with an operational control tower	Required
E	Varies; may begin at the surface, 700 ft AGL, or 1,200 ft AGL	Airports, transitions, and en route airspace	Required inside a surface area designated for an airport
G	Surface to the base of overlying Class E	Everything not designated A through E	Not required

The vertical figures come from the FAA's Aeronautical Information Manual (AIM). Treat them as orientation, not as a substitute for the chart or app for your location, because every airport's airspace is individually tailored.

Class A — high altitude

The AIM defines Class A as airspace from 18,000 feet MSL up to and including FL 600, where all aircraft operate under instrument flight rules. Under Part 107 the standard maximum altitude is 400 feet above ground level (or 400 feet above a structure when the aircraft stays within a 400-foot radius of it), so ordinary small-drone flight does not come near Class A.

Class B — major airport cores

Class B surrounds the busiest airports in terms of instrument operations or passenger numbers. The AIM describes it as extending from the surface to 10,000 feet MSL, built from a surface area and two or more layers, which is why some Class B areas resemble upside-down wedding cakes. An ATC clearance is required for all aircraft. For drones, prior authorization is required, and this is the most tightly controlled of the classes you are likely to meet. Each layer has its own boundaries, so check the exact point where you plan to fly rather than the airport name alone.

Class C — mid-size airports

Class C generally extends from the surface to 4,000 feet above the airport elevation around airports that have an operational control tower, are served by radar approach control, and have a certain number of instrument operations or passenger enplanements. A typical layout has a 5 nautical mile radius core from the surface and a 10 nautical mile radius shelf that starts no lower than 1,200 feet. Drone flight needs prior authorization, most often requested through LAANC. Our guide on what LAANC is explains how that works.

Class D — smaller towered airports

Class D generally extends from the surface to 2,500 feet above the airport elevation around airports with an operational control tower, but without the Class C structure and approach-control setup. The AIM calls its dimensions individually tailored, so there is no single radius to memorize. Prior authorization is still required.

Class D can be part-time. The AIM notes that when a Class D surface area is part-time, the airspace may revert to a Class E surface area or to Class G when the tower is closed. Do not assume that a closed tower means free airspace; check which classification applies at the time you plan to fly.

Class E — controlled airspace that is not A through D

Class E is the controlled airspace that is not Class A, B, C, or D. It exists in several forms, and only some of them trigger the drone authorization requirement:

Surface areas extend upward from the surface, usually around airports without a control tower that have instrument procedures. The authorization rule explicitly covers the lateral boundaries of a Class E surface area designated for an airport.
Extensions to Class B, C, D, and E surface areas begin at the surface and reach up to the overlying controlled airspace.
Transition areas begin at 700 feet or 1,200 feet above ground level. In most areas the Class E base is 1,200 feet AGL.

The sentence in 14 CFR 107.41 names surface areas designated for an airport, not Class E that begins above the ground. That is why a drone flying at 400 feet or lower under a Class E floor of 700 or 1,200 feet generally sits in Class G. The details are easy to misread on a chart, so confirm with an approved app rather than guessing.

Class G — uncontrolled airspace

The AIM defines Class G as the airspace not designated as Class A, B, C, D, or E, and the PHAK describes it as extending from the surface to the base of the overlying Class E. Most rural and many suburban areas fall here. The FAA's guidance for recreational flyers says to fly at or below 400 feet in Class G. Part 107 pilots do not need ATC authorization there either, but all other Part 107 rules (altitude, visual line of sight, Remote ID where applicable) still apply fully. The FAA states that there is no such thing as unregulated airspace in the National Airspace System.

Airspace class is not the whole picture

Even in Class G you still need to look at other layers:

Temporary flight restrictions can close an area regardless of class.
NOTAMs can announce hazards or restrictions that no chart shows.
Special use airspace, national parks, and critical infrastructure appear in FAA-approved apps and carry their own rules.
Your own certificate or exception conditions, summarized in our Part 107 explainer, still govern the flight.

How to check which class you are in

Use an FAA-approved B4UFLY or LAANC app, or a current sectional aeronautical chart. The FAA's B4UFLY service shows controlled airspace, special use airspace, airports, national parks, and temporary flight restrictions together with a status indicator. The FlyDroneMap dashboard shows an FAA UAS Facility Map altitude ceiling for U.S. locations, and the U.S. regulations page summarizes the main rules. Both are informational. Authorization itself comes only from an approved LAANC provider or FAA DroneZone.

Common mistakes

Judging by appearance. Airspace boundaries rarely line up with visible landmarks, and an open field can be inside a surface area tied to a small airport.
Treating a missing control tower as proof of Class G. A non-towered airport with instrument procedures can have a Class E surface area.
Assuming a part-time Class D is open when the tower is dark, without checking which class applies at that hour.
Believing Class G removes all rules. The altitude, line-of-sight, and TFR rules remain.
Using an old chart. Airspace is revised, so use current data.

FAQ

Do recreational flyers need authorization in the same classes as Part 107 pilots?

Yes. The recreational exception in 49 U.S.C. 44809 requires prior authorization in Class B, C, D, and within the lateral boundaries of a Class E surface area designated for an airport, the same places named in 14 CFR 107.41.

Do I need authorization in Class G?

No ATC authorization is required in Class G. You must still follow the altitude limit, keep the drone within visual line of sight, and respect any TFR or other restriction.

Why does Class E confuse so many pilots?

Because Class E begins at different heights in different places. Only Class E surface areas designated for an airport trigger the authorization requirement, so look at the exact location, not at the label alone.

Can an app replace a sectional chart?

An FAA-approved app is the practical tool, and the FAA itself points pilots to B4UFLY. If the result looks surprising or the data seems stale, verify against a current chart or the official FAA sources before you fly.