Proposed FAA Small UAS Rule — What is Class B, C, D, and E airspace?

Ben Marcus
Los Angeles Terminal Area Chart showing Class B, C, D, E, and G airspace boundaries

The long-awaited FAA Notice of Proposed Rulemaking (NPRM) on small-unmanned aircraft systems was issued on February 15, 2015. The reception from the drone community has been mixed. Although there are a few significant disappointments, such as a prohibition on beyond line-of-sight operation, one very pleasant surprise is a provision allowing small drones to operate in certain controlled airspace.

Section 107.41(b) of the proposed rule would allow for operation in Class B, C, D, or E airspace with prior authorization from air traffic control (ATC). I thought it might be helpful to the operator community to explain a little about the differences between controlled and uncontrolled airspace and what exactly Class B, C, D, and E airspace areas are.

What is the difference between controlled airspace and uncontrolled airspace?

Airspace is broadly categorized as either controlled or uncontrolled. In the United States, Class A, B, C, D, and E airspace is controlled. Class G airspace is uncontrolled.

In controlled airspace, air traffic controllers are responsible for separating aircraft flying under instrument flight rules (IFR) from one-another. In uncontrolled airspace, ATC does not provide that service. The distinction of controlled and uncontrolled airspace has nothing to do with whether the Federal Aviation Regulations (FARs) are enforceable or not; the FARs are in effect in all U.S. airspace.

If you’re flying on an airliner, your flight is most likely on an instrument flight plan, flying under IFR, and being flown in controlled airspace. There are rare occasions in remote areas where air carrier flights operate in uncontrolled airspace or under visual flight rules (VFR), but this is pretty unusual. In controlled airspace, ATC is responsible for maintaining sufficient separation between your aircraft and other aircraft flying under IFR. Whenever in visual conditions, even while operating under IFR, pilots are still required to see-and-avoid other air traffic.

Simply speaking, flying under IFR allows a pilot to fly into clouds and areas of reduced visibility. Under VFR, pilots must respect specified cloud clearance and visibility requirements.

FAA Flight Plan Form

ATC is generally not responsible for separating flights under VFR. In much of the U.S. airspace, flights operating under VFR are not required to have an altitude-reporting transponder. ATC can’t provide much assistance with respect to these flights, so the responsibility to maintain separation from other aircraft (including avoiding aircraft flying under IFR), rests with pilots.

Sometimes, ATC makes flight following service, sometimes referred to as traffic advisories, available to pilots flying under VFR in controlled airspace. However, the ultimate responsibility for maintaining separation remains with the pilots.

Air traffic control tower in Brussels

In uncontrolled (Class G) airspace, ATC does not provide separation services to aircraft. Appropriately rated pilots may operate under IFR in uncontrolled airspace without a flight plan or ATC clearance.

Class A Airspace

Class A airspace blankets the country between 18,000 feet and 60,000 feet (FL600). With very limited exceptions, all aircraft operating in this airspace are operating under IFR and are under positive control of air traffic controllers. Aircraft must have 2-way radio communications equipment and must have received an ATC clearance to enter Class A airspace. The NPRM would prohibit flight of small UAS in Class A airspace.

Class B Airspace

Class B airspace surrounds our country’s busiest international airports, like those in Los Angeles, San Francisco, Chicago, and New York. Like in Class A airspace, ATC clearance is required to enter Class B airspace. When flying under VFR, a pilot must hear the words “Cleared into the Class Bravo airspace” before entering. Aircraft must be equipped with an altitude-reporting transponder whenever flying within 30 nautical miles of any Class B airport. There are other requirements, as well. For example, a student pilot on a solo flight may not enter Class B airspace unless the student has previously received flight instruction in that particular Class B airspace area and has received a logbook endorsement from his or her flight instructor permitting flight in that airspace.

A view inside the control tower at London Heathrow

Class C Airspace

Class C airspace surrounds busy airports, but not quite as busy as Class B airports. Some examples of Class C airports include Burbank, Ontario, and John Wayne in Southern California, San Jose and Oakland in Northern California, Midway in Chicago, and Islip near New York City. Other examples include Daytona Beach, Florida, Peoria, Illinois, and Little Rock, Arkansas. An ATC clearance is not required for manned aircraft to enter Class C airspace, however pilots must establish 2-way radio communications with ATC prior to entering. Also, aircraft must have an altitude-reporting transponder to operate within or above Class C airspace. Like at Class B airports, air traffic controllers at Class C airports have radar, so understanding what altitude each aircraft is flying at is important.

Class D Airspace

Class D airspace surrounds many general aviation airports and some that have limited air carrier traffic. Examples include Santa Monica, Palo Alto, and San Carlos in California, Dupage near Chicago, and Teterboro near New York City. Other examples include Gainesville, Florida, Columbus, Georgia, and my alma mater’s airport in West Lafayette, Indiana (Go Boilers!). As with Class C airspace, no clearance is required, but 2-way radio communication must be established with ATC prior to entering Class D airspace. Air traffic controllers at these airports may or may not have radar and no altitude-reporting transponder is required (unless otherwise required because of proximity of a Class B airport). Often, these controllers rely upon position reports from pilots until the aircraft are close enough for them to see visually from the control tower.

Air traffic control tower at Santa Monica Airport

It is important to understand that an air traffic controller’s primary responsibility with respect to aircraft near an airport is to separate traffic on the runway. Aircraft in the air must not rely on controllers for separation. Pilots are always responsible to see-and-avoid other aircraft. The smaller the aircraft is, the harder it is to see.

Class B, C, and D airports have control towers. However, most airports in the United States do not have control towers and exist within Class E or Class G airspace. At these airports, pilots self-report their positions on a Common Traffic Advisory Frequency (CTAF).

Class E Airspace

Class E airspace is all the rest of the controlled airspace not already described. Most of this airspace is not near the surface, but aloft, where aircraft flying under IFR are in the en route segment of flight. Over most of the country, the base of Class E airspace is at either 700 or 1,200 feet above the ground, so this isn’t an issue for small UAS operating at 500 feet and below. However, some airports without control towers have an area of Class E airspace that extends down to the surface. This is in place to protect aircraft departing and arriving under IFR. At these airports, airspace designers determined that Class G uncontrolled airspace would not provide sufficient levels of safety, specifically aircraft separation, for departing and arriving instrument traffic. Also, some airports with operating control towers have Class E surface areas that extend beyond the lateral limits of the associated Class C or D airspace. It is all of these Class E surface areas associated with airports that the NPRM specifies as requiring prior authorization from ATC for small UAS to enter.

Example of Class E surface area associated with an airport

Why is this important?

The NPRM has provided quite a bit of flexibility for small UAS operations, but the FAA does not want to compromise safety of manned aircraft operations, and neither do any of us in the drone community. The National Airspace System is designed to maximize safety while making flight operations as efficient as possible. Remaining clear of an arbitrary radius around an airport doesn’t make much sense. Sometimes, runways are oriented in such a way that air traffic tends to be rather linear inbound and outbound from the airport. Air traffic does not get distributed equally in the areas surrounding the airport. As an example, at Los Angeles International Airport (LAX), the four runways are oriented parallel to each other in an east/west direction. The surface area of the Class B airspace extends quite far to the east and west, where arriving and departing aircraft are descending and climbing, but areas just one mile to the north and south of the runways and below 700 feet are in Class G uncontrolled airspace.

Los Angeles Class B airspace outlined with thick blue lines.

In conclusion, it’s a good sign that the FAA is willing to allow small UAS operations in controlled airspace with ATC authorization. I hope this makes it through to the final rule. Without this capability, drone flights would be extremely limited in urban areas, which are mostly blanketed by controlled airspace. It is important that operators respect these and all of the final rules to assure separation from manned aircraft. At NoFlyZone.org, we’re committed to providing the drone community with an easy-to-use, comprehensive airspace database that will make it easy for operators to know what type of airspace they’re operating in and whether or not ATC clearance is required.

To learn more about airspace, visit your local FAA-certified flight or ground instructor or read more in the Aeronautical Information Manual.

Future of Flight

and other random thoughts

    Ben Marcus

    Written by

    Ben is cofounder & Chairman of AirMap. helping make flight part of daily life. He is an FAA-certified Airline Transport Pilot and Flight Instructor.

    Future of Flight

    and other random thoughts

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