What Is Controlled Airspace?

In the simplest terms, controlled airspace is exactly what it sounds like – airspace that is controlled by some sort of government authority. Controlled airspace doesn’t mean the aircraft in it are necessarily under the control of, or otherwise receiving services from, air traffic control (ATC) but it does provide a number of considerations for both professional and recreational pilots. 

Controlled airspace brings to bear different requirements in weather conditions and, in some cases, aircraft equipment and pilot certifications. Particularly if a pilot is venturing to a new area they’re unfamiliar with, a review of the airspaces to be encountered can prevent everything from embarrassment to FAA action.

How Does Controlled Airspace Work?

Controlled airspace is airspace in which air traffic control can provide services for aircraft. Their ability to provide these services, such as clearances for IFR (instrument flight rules) aircraft or flight following for VFR traffic, will vary depending on the particular location and airspace type.

How Is Airspace Classified?

In the United States, all national airspace is classified as either Class A, B, C, D, E, or G. Any particular location can only be classified as a single airspace at a time.

What Classes of Airspace are Considered Controlled Airspace?

Classes A, B, C, D, and E are controlled, though the requirements to operate in each airspace differ slightly.

Can You Fly in Controlled Airspace?

Yes – controlled airspace is available for the use of civilian and military aircraft at all times, provided the regulatory requirements for entry are met.

What Airspace Requires Clearance?

Class A and B airspace both require specific clearance to enter. Class C and D require communication to be established between the aircraft seeking entry and the controlling authority.

What Is the Difference Between Controlled and Uncontrolled Airspace?

In controlled airspace, air traffic control can provide services to aircraft in the airspace to the extent practical. In uncontrolled airspace, air traffic control services are unavailable. 

It’s important to note that the delineation of controlled versus uncontrolled airspace on a chart (controlled airspace map) does not necessarily align with the ability to talk to air traffic control or even be seen on radar. In some situations, a pilot may be able to talk to ATC but be in uncontrolled airspace and unable to receive any controlling services.

What Is Important to Consider for Controlled Airspace?

The different classes of controlled airspace have their own requirements in terms of weather requirements for pilots operating under visual flight rules (VFR) and, in some cases, requirements for aircraft equipment and pilot certification requirements.

Entry Requirements

Class B, C, and D airspace all have particular entry requirements requiring certain levels of communication with ATC prior to entering the airspace. 

It’s important to remember airspaces are heavily catered to their local area and may be shaped in unusual ways or be established utilizing non-standard altitudes and may overlap one another. So a proper briefing can help pilots plan for the requirements long before arriving at the airspace boundaries.

Equipment

While a handheld or portable radio might be sufficient for making contact with ATC, additional aircraft equipment detailed below must be installed and operative for operation in some airspace classes.

Minimum Pilot Certification

Most controlled airspace is open to even student pilots but as we progress to larger and busier airspaces the requirements tighten. Both Class A and B airspaces have requirements for minimum pilot certification level and/or endorsements.

Visual Flight Rule Weather Minimums

One of the more confusing things for new pilots can be learning the variety of weather minimums each airspace requires. 

With the exception of Class A, each class of airspace has certain minimum flight visibility (the distance a pilot can see from the aircraft) as well as minimum cloud clearance requirements a pilot must maintain, even when under the control of ATC.

Types of Controlled Airspace

Depending on location, controlled airspace may start as low as the ground or as high as 14,500 feet in the United States. 

With each airspace having varying requirements for pilots and weather, it’s important to be aware of classes you might potentially encounter on and flight.

Class A

Class A airspace is only for the use of aircraft under instrument flight rules (IFR). All operations in Class A airspace use the standard altimeter setting of 29.92 inches of mercury to ensure proper separation of aircraft across large swaths of airspace. 

Due to the use of standardized pressure altitude, Class A altitudes are referred to as ‘flight levels’ and shortened into three-digit numbers. For example, 24,000 feet becomes flight level 240 (abbreviated FL240). In the United States class A airspace ranges from FL180 (approximately 18,000 feet) to FL600 (approximately 60,000 feet).

Requirements for Airspace Operation:

• Entry Requirements: Aircraft must be on an IFR flight plan and cleared between FL180 and FL600.
• Equipment: The aircraft must have a two-way radio, an altitude reporting transponder, and ADS-B “out” broadcasting equipment. At or above FL240, the aircraft must be equipped with distance measuring equipment (DME) or an IFR-approved area navigation system such as GPS. 14 CFR 91.205 details the specific IFR equipment requirements.
• Minimum Pilot Certificate: Private pilot certificate with an instrument rating.

Basic VFR Weather Minimums: 

• Flight Visibility: None, as all aircraft in Class A are operating under IFR.
• Distance from Clouds: None, as all aircraft in Class A are operating under IFR.

Class B

Class B is designated only around the 37 busiest airports in the United States. Generally shaped like an upside-down tiered wedding cake starting at the surface and ending at 10,000 feet above the ground, “bravos” encompass some of the busiest airspaces in the world, frequently centered around large airline hub airports. 

Some Class B airspaces, such as New York, include multiple major airports and require pilots to remain attentive to air traffic control instructions and the multitude of fast-moving jet aircraft.

Requirements for Airspace Operation:

• Entry Requirements: A specific clearance to enter Class B airspace is required, in addition to two-way radio communication.
• Equipment: A two-way radio is required in addition to an altitude reporting transponder as well as ADS-B “out” broadcasting equipment.
• Minimum Pilot Certificate: A private pilot certificate is generally required to enter Class B, but a student pilot can be endorsed by his or her flight instructor for flight into a particular Bravo. The requirements for, and limitations to, this endorsement are covered in 14 CFR 61.95. Additionally, Sport pilots can be endorsed for operations in Class B airspace, not restricted to a particular Bravo.

Basic VFR Weather Minimums: 

• Flight Visibility: 3 statute miles
• Distance from Clouds: “Clear of clouds”. Due to the high volume of aircraft in Class B, only requiring aircraft to remain clear of clouds (as opposed to a certain distance) allows for more consistency in their maneuvering and flying of assigned heading or altitudes.

Class C

Class C airspace is located around approximately 120 busier airports but in areas that lack the volume to justify being classified as Class B. Class C airspace generally has an inner ring with a 5 nautical mile radius, covering the surface to 4,000 feet above ground level (AGL). Surrounding this is an outer ring, generally to a 10 nautical mile radius, from 1,200 feet AGL to 4,000 feet AGL. In some areas, two areas of Class C may touch and form a figure-8 shape. 

An example of this would be Oklahoma City where both the main civilian and military airports have Class C airspaces based around them, sharing an outer ring. All Class C airspaces will have air traffic control of the surrounding area in the form of a Terminal Radar Approach Control (TRACON) facility.

Requirements for Airspace Operation:

• Entry Requirements: Two-way radio communication is required. “Two way” means both the ground and aircraft have acknowledged each other by callsign. A controller responding to your initial call with “Piper 123AB, go ahead with your request” is two-way, while a response of “Piper calling, say again” is not.
• Equipment: A two-way radio is required along with an altitude reporting transponder.
• Minimum Pilot Certificate: A student pilot or better certificate allows entry into Class C. A Sport Pilot can enter Class C if they’ve received the appropriate endorsement.

Basic VFR Weather Minimums: 

• Flight Visibility: 3 statute miles
• Distance from Clouds: 500 feet below, 1,000 feet above, and 2,000 feet horizontally from any cloud.

Class D

Class D airspace surrounds the area of an airport with an operating control tower and is shown on a sectional chart with a hashed blue circle. Class D generally extends from the surface to 2,500 feet AGL but the size and shape of the airspace can vary to “allow for safe and efficient handling of operations”. Frequently a towered airport unaffected by obstacles or unusual procedures will be a simple circular airspace with a 4-mile radius, centered on the airport. 

Occasionally a small area will jut out of the circular airspace to protect an instrument approach procedure. This area may be a continuation of the Class D or may be a small area of Class E airspace to the surface (detailed in the next section). If a control tower closes overnight, the Class D airspace will revert to Class E or G.

Requirements for Airspace Operation:

• Entry Requirements: Two-way radio communication is required prior to entry.
• Equipment: A two-way radio is the only aircraft equipment required.
• Minimum Pilot Certificate: A student pilot certificate allows entry into Class D. A Sport Pilot can enter Class D if they’ve received the appropriate endorsement.

Basic VFR Weather Minimums: 

• Flight Visibility: 3 statute miles.
• Distance from Clouds: 500 feet below, 1,000 feet above, and 2,000 feet horizontally from any cloud.

Class E

Class E is somewhat unique airspace because it is defined as controlled but unlike the previously mentioned airspaces does not actually require VFR aircraft to be utilizing air traffic control services. The altitudes of Class E can also vary significantly depending on the location but the overwhelming reason for the variety is to allow the control of IFR aircraft as required by different locations.

Generally speaking, outside of mountainous areas Class E airspace starts at 1,200 feet AGL. Additionally, at many airports, the Class E can extend down to 700 feet AGL in a “Class E transition area” to help separate IFR and VFR traffic, marked on charts with a magenta shaded area. At some airports, the Class E can even extend to the surface, denoted by a hashed magenta circle. In a few areas, due to limited radar coverage, Class E starts at 14,500 feet. 

In all cases, Class E extends to the base of the overlying airspace, whether it be class A, B, or C. Additionally, the airspace above FL600 (the ceiling of Class A airspace) is designated as Class E.

Requirements for Airspace Operation:

• Entry Requirements: None.
• Equipment: To operate above 10,000 feet your aircraft must be equipped with an altitude reporting transponder and ADS-B “out”. Below 10,000 feet, if you are intending to utilize ATC services, a two-way radio is needed.
• Minimum Pilot Certificate: No specific requirements are in place.

Basic VFR Weather Minimums: 

• Flight Visibility: Below 10,000 feet: 3 miles. Above 10,000 feet: 5 miles.
• Distance from Clouds: Below 10,000 feet: 500 feet below, 1,000 feet above, and 2,000 feet horizontally. Above 10,000 feet: 1,000 feet below, 1,000 feet below, and 1 mile horizontally.

It’s Always A Good Time To Review Controlled Airspace 

Airspace can be confusing for both new and experienced pilots. The variety of equipment and weather requirements can lead to frustration for student pilots trying to prepare for their checkrides and can leave pitfalls for even experienced pilots, particularly those undertaking new routes and destinations. Utilizing resources from the FAA and industry can help pilots of all levels to remain up to date on changes in airspace and the requirements to utilize it.

FLYING Magazine provides resources for pilots in all stages of flight training and flying. To stay informed on all of the latest in Aviation, subscribe to the FlyingMag newsletter today.