What Are Airspace Classes?

To handle all the traffic flying in the sky in a safe and consistent manner, the FAA developed the National Airspace System. It divides the sky into sectors that serve different volumes of traffic or contain specific activities. Each airspace has different operational rules, pilot responsibilities, and even weather requirements to operate.

How are Airspace Classes Classified?

The National Airspace System divides up the classifications of airspace based on:

  1. The volume of air traffic
  2. The type of operations conducted
  3. The required level of safety
  4. National and public interest

Controlled Airspace vs. Uncontrolled Airspace

There are two categories of airspace or airspace areas: regulatory and non-regulatory. Regulatory airspace has a set of specific regulations that govern that area; whereas non-regulatory airspace is just used to advise or warn pilots of the operations that are conducted within the airspace.

Regulatory airspace consists of:

  • Classes A, B, C, D, E, and G
  • Restricted areas
  • Prohibited areas

Non-Regulatory airspace consists of:

  • Military operations areas (MOAs)
  • Warning areas
  • Alert areas
  • Controlled firing areas

Within these two categories, there are four types:

  1. Controlled
  2. Uncontrolled
  3. Special use
  4. Other airspace
Courtesy: FAA

Airspace Classes

Various charts help pilots figure out which airspace they are in. The most common chart is the sectional chart, which is a map for pilots. Sectional charts provide detailed information that includes airspace classes. Each of the different types of airspace has specific requirements that must be met to operate in it.

Class A Airspace

Class A airspace begins at 18,000 feet above sea level known as mean sea level, or msl, and goes up to 60,000 feet msl. This airspace covers both the 48 contiguous states and Alaska and extends offshore 12 nautical miles. Most of the traffic operating in class A airspace will be commercial airlines or corporate and military jets. Class A airspace is not depicted on the visual flight rules (VFR) charts, because all the aircraft that operate in Class A airspace are required to be operating according to instrument flight rules (IFR).

IFR/VFR: IFR only

Altitude Range: 18,000 feet msl up to and including 60,000

Speed Restrictions: No speed limit except remain slower than the speed of sound

Need ATC Clearance?: Yes

Other Characteristics:

  • Mode-C transponder
  • Maintain two-way radio communication with ATC
  • Distance measuring equipment required above 24,000 feet msl
  • Anytime above 18,000 feet msl, or in Class A, or, altimeter should be set to 29.92

Class B Airspace

Class B, or Bravo, airspace surrounds the nation’s busiest and largest airports. The main airport that a Class B area has been designated for is considered the primary airport. There can also be other smaller airports within Class B, which are designated as secondary airports. On a VFR sectional chart, look for the solid blue lines to find Class Bravo airspace. The altitudes shown on VFR sectional charts are labeled in msl.

IFR/VFR: Both

The visibility must not be any less than 3 statute miles; the pilot must remain clear of clouds.

Altitude Range

Vertically: Located between the surface and 10,000 feet msl, with some exceptions.

Laterally: Distances of the airspace will vary with the local area, with several layers.

A 30-mile ring, known as a Mode-C Veil, surrounds the primary airport of Class B airspace. Class B, because of all the altitude tiers, is sometimes referred to as an upside-down wedding cake.

Speed Restrictions:

There are two speed limitations in Class B airspace:

  • When operating below 10,000 feet msl, the speed limit is 250 knots
  • When operating below Class B airspace, the speed limit is 200 knots

Need ATC Clearance?: Yes

To operate in Class B airspace:

  • A clearance to enter the airspace must be given to the pilot.
  • Must be at least a private pilot, or a student pilot with the correct endorsements.
  • Two-way communication with ATC must be maintained.

Other Characteristics

  • Aircraft must operate with a Mode-C transponder within the 30-mile Mode-C veil, even if they are not necessarily inside of Class B airspace. 
  • Mode-C veil is labeled “30 NM Mode C” with a solid magenta line on a sectional chart.

Class C Airspace

Class C, or Charlie, airspace is designated for airports that are not as busy as Class B, but are still busy enough to require radar approach assistance to organize and separate aircraft traveling into and out of the local area. Class C is labeled on a VFR sectional chart using solid magenta lines.

IFR/VFR: Both

To operate VFR inside Class C, visibility must be greater than 3 statute miles and a pilot cannot fly any closer to the clouds than 500 feet below, 1,000 feet above, and 2,000 feet horizontally.

Altitude Range

The shape of Class C airspace generally has two cylinders—the inner core, and the outer shelf.

  • The inner core has a diameter of 5 nm, and extends from the surface up to 4,000 feet above ground level (agl).
  • The outer shelf is a 10 nm area, from 1,200 feet agl to 4,000 feet agl.

Speed Restrictions:

  • Any time operating below 10,000 feet msl, the speed limit is 250 knots. 
  • Below 2,500 feet agl within 4 nm of the primary Class C airport, the limit is 200 knots.

Need ATC Clearance?: No

  • No specific clearance is required, but two-way communication with ATC must be established. 
  • If the controller responds to your initial call with your call sign, you are cleared to enter the airspace, unless told to “Remain clear of Class Charlie.”

Other Characteristics:

  • At least be a student pilot
  • Aircraft must possess a Mode-C transponder.

Class D Airspace

Class D, or Delta, airspace is controlled airspace surrounding smaller local airports that are quiet enough not to require any radar separation, but still busy enough to require a control tower. Class D is labeled on a VFR sectional chart using dashed blue lines. The altitudes shown on VFR sectional charts are labeled in msl.

IFR/VFR: Both

To operate VFR inside Class D, visibility must be greater than 3 statute miles, and a pilot cannot fly any closer to the clouds than 500 feet below, 1,000 feet above, and 2,000 feet horizontally.

Altitude Range

  • Class D is a single cylindrical area, extending from the surface to 2,500 feet agl. 
  • If underneath Class B or C airspace, Class D extends to the floor of the airspace above.
  • Class D airspace radius is typically 4.4 nm, but can be between 3 and 7 miles depending on how much IFR traffic the airport has. The more IFR traffic, the bigger the airspace to accommodate it.

Speed Restrictions

  • Anytime operating below 10,000 feet msl, the speed limit is 250 knots. 
  • Below 2,500 feet agl within 4 nm of the Class D airport, the limit is 200 knots.

Need ATC Clearance?: No

  • However, two-way communication with the tower must be established. 

Other Characteristics

  • Must be at least a student pilot.

Class E Airspace

Class E, or Echo, airspace is defined as controlled airspace that is not Class A, B, C, or D and is one of the largest parts of the national airspace system. There are seven unique types or locations of Class E airspace. These various types of Class Echo airspace can be found on sectional and other low-altitude charts as long as that airspace begins below 14,500 feet msl.

IFR/VFR: Both

  • Below 10,000 feet msl, the visibility must be at least 3 statute miles, and pilots cannot be any closer to clouds than 500 feet below, 1,000 feet above, and 2,000 feet horizontally. 
  • At or above 10,000 feet msl, the visibility must be at least 5 statute miles and pilots cannot be closer to clouds than 1,000 feet above, 1,000 feet below, and 1 statute mile horizontally.

Altitude Range

No defined vertical limits to Class Echo. Class E either starts at the surface or a defined altitude, and continues upward until coming in contact with a different class of controlled airspace. The seven types of Class Echo airspace:

  • Surface Area Designated For an Airport: Configured to contain any instrument procedures for that particular airport. It is depicted on a VFR sectional chart with a dashed magenta line and begins at the surface. 
  • Extension to a surface area: Extensions to Classes B, C, or D to allow for instrument approach procedures into an airport. Also depicted with a dashed magenta line, but does not surround an airport.
  • Transition Airspace: Used to transition aircraft to or from the terminal area and en-route environments. On sectional charts, A wide magenta line, hard on one side, soft on the other, indicates the floor of Class E at 700 feet agl, and a wide blue line, hard on one side and shaded on the other indicates the floor at 1,200 feet agl. Additionally, in the absence of the shaded blue like the hard side of the magenta line is where Class E airspace begins at 1,200 feet.
  • Federal Airways: Each airway is 8 nautical miles wide, and extends from 1,200 feet agl up to, but not including 18,000 feet msl.
  • Offshore Airspace Areas: Allows ATC to provide services to IFR traffic beyond 12 NM from the coast. On a sectional chart, it looks like a zipper, and the floor of each sector is indicated inside each respective area.
  • Other: Elsewhere, Class Echo does not start until 14,500 feet msl, except in areas within 1,500 feet of the ground. Class Echo goes upward to 18,000 feet, where Class Alpha starts, then continues at At FL600, where Class Alpha ends.
  • En Route Domestic Areas: Located outside any federal airway, allowing ATC to separate traffic. 

Speed Restrictions

  • Above 10,000 feet msl, slower than the speed of sound.
  • Anytime operating below 10,000 feet msl, the speed limit is 250 knots. 
  • Below 2,500 feet agl within 4 nm of the Class D airport, the limit is 200 knots.

Need ATC Clearance?: No

Other Characteristics

  • No specific pilot qualifications
  • No equipment requirements
  • No operational procedures necessary

Class G Airspace

Class G, or Golf, airspace is considered uncontrolled, and makes up the rest of the area that isn’t already Class A, B, C, D, or E. Class G will start at the surface and continue upward until reaching 1,200 feet agl, which is where Class Echo’s en-route domestic areas typically start.

IFR/VFR: VFR

Flying below 1,200 feet agl

  • During the day, regardless of the msl altitude, aircraft must remain clear of clouds.
  • At night, the visibility must be at least 3 statute miles and cloud clearances are 500 feet below, 1,000 feet above, and 2,000 feet horizontal. 

Flying above 1,200 feet agl, but less than 10,000 feet msl

  • During the day, visibility should be 1 statute mile and cloud clearances are 500 feet below, 1,000 feet above, and 2,000 feet horizontal. 
  • At night, the visibility must be at least 3 statute miles, and pilots cannot be any closer to clouds than 500 feet below, 1,000 feet above, and 2,000 feet horizontally. 

Flying both above 1,200 feet agl and 10,000 feet msl

  • Day and night, the visibility must be at least 5 statute miles and pilots cannot be closer to clouds than 1,000 feet above, 1,000 feet below, and 1 statute mile horizontally.

Altitude Range: Anything below Class Echo

Speed Restrictions

  • Above 10,000 feet msl, slower than the speed of sound.
  • Anytime operating below 10,000 feet msl, the speed limit is 250 knots. 
  • Below 2,500 feet agl within 4 nm of the Class D airport, the limit is 200 knots.

Need ATC Clearance?: No

Other Characteristics

  • No specific pilot qualifications
  • No equipment requirements
  • No operational procedures necessary

Other Airspace Classes Worth Mentioning

In addition to the six classes of airspace mentioned above, there are other types of airspace. They fall into a category called special use airspace. Special use airspace consists of areas wherein certain activities are being conducted that must be confined to that area, or wherein limitations are imposed upon other aircraft that are not a part of those activities, or both. Special use airspace areas are depicted on aeronautical charts, except for controlled firing areas. 

For regulatory special use airspace, there are prohibited areas and restricted areas. Non-regulatory special use airspace consists of warning areas, military operating areas, alert areas, and controlled firing areas.

Prohibited Areas

Prohibited areas exist where aircraft are not permitted to fly for either security reasons or to protect national welfare. It begins at the surface and extends up to a specified altitude, and is depicted on sectional charts with a blue hashed shape with the letter “P” and a series of numbers, to serve as the identifier of that area.

Restricted Areas 

Restricted areas contain hazardous activities to non-participating aircraft, such as artillery firing, aerial gunnery, or guided missiles. Aircraft are not allowed to fly within the area when it is active unless they have permission. It begins at the surface and extends up to a specified altitude, and is depicted on sectional charts with a blue hashed shape with the letter “R” and a series of numbers, to serve as the identifier of that area.

Warning Areas 

Warning areas also contain hazardous activities to non-participating aircraft, and warn nonparticipating pilots of potential danger, without preventing them from operating within that area. There are over domestic and international waters, three nautical miles from the coast. It begins at the surface and extends up to a specified altitude, and is depicted on sectional charts with a blue hashed shape with the letter “W” and a series of numbers, to serve as the identifier of that area.

Military Operation Areas (MOAs) 

Military operating areas, or MOAs, contain military activities and serve to separate certain military training from IFR traffic. VFR traffic may still fly through the area whether it is in use or not but should exercise caution. MOAs start at a designated altitude and extend up to, but not including FL180 and are depicted on sectional charts using magenta hashed lines and are given names such as “Rainier MOA”, “Chinook MOA”.

Alert Areas

Alert areas inform pilots of areas that have high volume traffic usually due to pilot training, or an unusual type of aerial activity. Transitory aircraft should use extra caution in these areas. Alert areas on a sectional chart are depicted with magenta hashed lines, with the letter “A,” and a series of numbers that serve as the identifier. 

Controlled Firing Areas

Controlled firing areas, or CFAs, allow such activity to take place in a confined area to not create a hazard to aircraft. Unlike other hazardous activities that cordone off specified airspaces, activities are immediately suspended when a nonparticipating aircraft appears to be approaching the area. CFAs aren’t charted since they do not require pilots to alter their course.

Temporary Flight Restriction (TFR)

Temporary flight restrictions are short-term blocks of airspace used to temporarily prevent or limit nonparticipating aircraft from entering that area. They are usually used for spacecraft launches, natural disaster relief, forest fires, sporting events, or to protect prominent public figures. 

Other Airspace

Other auxiliary airspaces include airport advisory areas, air defense identification zones, military training routes, VFR flyways, VFR corridors, VFR transition routes, terminal radar service areas, national security areas, and finally, U.S. Wildlife refuges, parks, and forest service areas.

Know Your Airspace Rules

Every time you get into an aircraft, you are surrounded by airspace. It is important to understand the rules and requirements so that you can safely and legally. Subscribe to FLYING Magazine to learn more. 

FAQ 

What Is Controlled Airspace?

Controlled airspace is an airspace of defined dimensions within which air traffic control (ATC) services are provided.

What Are the Different Classes of Airspace? 

In the U.S., airspace is categorized as regulatory and non-regulatory. Within these categories exist: controlled (Classes A, B, C, D, and E) and uncontrolled (Class G) airspace, based on which air traffic control service is provided to IFR flights and some VFR flights. There are also other types of airspace including “special use” and “other airspace.”

What Is Class G Airspace?

Class G, or Golf, airspace is considered uncontrolled and makes up the rest of the area that has not been designated already as Class A, B, C, D, or E.

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