Airspace Classes

Airspace Classes and Special Use Airspace

Captain Judy’s Corner: Airspace Part 3


Knowledge of airspace classes is essential for all pilots. ICAO standardized these classes with rules and regulations. They include Class A, B, C, D, E, G, and special use airspace. Most importantly, these designations define clearance requirements, minimums, and dimensions. Pilots may need to adjust altitude and speed depending on the section of airspace they’re flying in. Also, ATC may require radio contact or communications. Because airspace categories differ, you must learn how to recognize them on charts. Furthermore, you must understand the detailed requirements of each. Besides, authorities established airspace classes to keep you safe. Above all, safety first!

How I Learned Airspace

Airspace may be one of the most complex and important topics that a pilot needs to understand. Learning airspace can seem overwhelming at first with a lot to remember. How did I tackle learning about airspace? I realized that for each airspace classification there are only 3 topics to remember: dimensions, equipment, and Visual Flight Rules (VFR) weather minimums. I then discovered some of these airspace dimensions have the same VFR weather minimums and equipment requirements. 

Student pilots were not always so fortunate to have the Internet or cell phones for studying. Students now use online flash cards to study airspace and other topics. I studied airspace before computers and cell phones. Making my own index cards, I placed the classification on the front. I then put the dimensions, weather minimums, and requirements on the back. I took these flash cards with me everywhere! Waiting in the grocery store line or having car maintenance? No problem – I had my flash cards. I purchased a cassette tape on airspace (today it’d be an MP3), and listened in the car or while doing housework. I focused every spare moment on learning airspace.

Airspace familiarization on the VFR Sectional Chart is equally important. I studied the sectional chart from the top to the bottom naming the classification and information for each airspace. Your airspace knowledge will come from determination, repetition, study, and focus.

Types of Airspace

First of all, the FAA has identified three types of airspace in the U.S. They are controlled, uncontrolled, and special use. Second, each category includes specific airspace use. For example, controlled airspace includes Class A, Class B, Class C, Class D, and Class E. Furthermore, uncontrolled airspace includes Class G. Lastly, special use airspace includes areas of concern, such as restricted or prohibited airspace.


In Airspace Part 1, I described airspace issues we faced during my world flight“We departed from Yerevan, Armenia (UDYZ) in the Citation jet and arrived into Tel Aviv, Israel (LLBG). My pre-flight briefing with the crew included news that, once airborne, we would receive a mandatory security stop. This would occur before being allowed into Israel airspace.”

Not All Airspace is the Same

Certainly, my world flight would have been unlikely without clearly designated airspace. Because of the efforts of the International Civil Aviation Organization (ICAO), flying internationally has become much safer. In 1941, the United Nations formed ICAO, and they established a standard, organized three-dimensional airspace system. This three-dimensional approach includes various rules and regulations. However, some nations chose a two-dimensional approach. 

For instance, China chose a two-dimensional approach. In China, each regional authority of the Civil Aviation Administration of China (CAAC) must approve civilian flights. Also, they must get approval by the military before issuing a flight permit. The three-dimensional approach is relevant to air traffic management. For instance, the United States, Europe, and many other nations use this.

National Aviation Authorities

A country’s aviation authority or similar authority determines how it uses the ICAO dimensional approach and classifications. For instance, some countries modified airspace classifications. This was because they addressed security, safety, or air traffic services that existed before ICAO standardization. However, most nations chose a version of the ICAO classification, whether using a three-dimensional or two-dimensional approach. ICAO airspace classes are: Class A, Class B, Class C, Class D, Class E, Class F, and Class G. 

The most widely modified class is Class F airspace. ICAO designated Class F as either uncontrolled or special use airspace (SUA). Like most countries, the United States established separate SUAs to meet security and safety requirements. Furthermore, SUAs in the U.S. remain mostly unchanged after initial implementation of the ICAO classifications.

Requesting Clearance

Due to safety concerns, the FAA established SUAs in the U.S. As a result, military operations, national security, and heavy flight training activities became safer. Therefore, non-participating aircraft are restricted from flying in these ares. These areas range from prohibited to caution, and this overview of U.S. SUA classifications begins with the most restrictive. Pilots have limited access, and as a result must request the appropriate clearance to enter certain areas. Most importantly, a flight chart (map) displays dimensions of the areas and minimum requirements.

Special Use Airspace Examples

A. Prohibited Area

Prohibited Areas are established for national security and welfare. A pilot must request clearance from the controlling agency before entering a Prohibited Area. For example, P-50 protects the U.S. Naval Submarine Base at Kings Bay, Georgia.

B. Restricted Area

Restricted Areas contain hazardous activity, such as testing of artillery, missiles, or aerial gunnery. Furthermore, the controlling agency requires clearance. For example, Restricted Area R- 4401 ensures military aircraft conducting high altitude training remain within the confines of that airspace.

C. Military Operations Area

Military Operations Areas (MOA) involve military training activities. Therefore, authorities warn non-participating aircraft to use extreme caution while flying within these areas. Pilots do not need to request clearance, but it is advisable to contact the controlling agency for current hazardous activity. For instance, Lemore MOA contains activities such as, air combat tactics, air intercepts, aerobatics, formation training, and low altitude tactics.

D. Warning Area

Warning Areas are located over domestic or international waters and generally 3 nautical miles surrounding the coasts. Hazardous activities can impact non-participating aircraft. However, no clearance is required to enter. For example, W497B protects airspace during spacecraft operations from Cape Canaveral. 

Temporary Flight Restrictions (TFR) temporarily restrict flight activity from operating within a defined area. This protects persons or property in the air or on the ground. The FAA issues TFRs based on the movement of the President or other essential government officials. TFRs can also include disaster relief operations, wildfire response, or large events, and they are issued by NOTAMs.

E. National Security Area

National Security Areas protect the safety and security of personnel on the ground. Authorities request flight activities avoid these areas. For example, a National Security Area would be a nuclear power plant.

F. Air Defense Identification Zone (ADIZ)

Air Defense Identification Zones (ADIZ) include monitored airspace. For example, authorities monitor the identification, location, and control of civil aircraft. This is in the interest of national security. Pilots must file under Instrument Flight Rules (IFR) or Defense Visual Flight Rules (DVFR) before entering or departing the U.S. This can be over land or water.

Airport Advisory Areas occur at non-towered airports with a Flight Service facility. Flight Service provides advisories upon request within 10 NM on the Common Traffic Advisory Frequency (CTAF).

G. Wildlife Refuge

A Wildlife Refuge is specific to land management for wildlife, such as migratory birds. Authorities request that pilots remain 2000’ above ground level (AGL). For example, the Merritt Island National Wildlife Refuge near Cape Canaveral, is a special use area.

H. Wildlife Sanctuary

A Wildlife Sanctuary is an area established to preserve a species. Authorities require flight activities to remain 1000’ AGL. In other words, do not disturb the wildlife!

I. Military Training Route

Military Training Routes contain military training activities along a specific route. Although no clearance is required, pilots may contact the controlling agency for current hazardous activity. As shown, the image with IR indicates military training by instrument reference. VR indicates visual training. Three numbers indicates training activities are above 1500’AGL, and four numbers indicates training at or below 1500’ AGL. 

J. Alert Areas

Alert Areas contain a high volume of flight activity. However, authorities do not require clearance to enter these areas. So, pilots must remain extra vigilant looking for traffic when in these areas.

Controlled Firing Areas (CFA) are not found on the Sectional Chart, but they are listed in the Chart Supplement Guide. Activities are conducted in a controlled environment that could be hazardous to nonparticipating aircraft. Again, authorities do not require clearance. However, a pilot may contact the controlling agency for the most current hazardous activity.

K. Terminal Radar Service Area (TRSA)

Terminal Radar Service Area (TRSA) provides advisories for visual flight rule (VFR) pilots in Class D airspace. This includes a high volume of instrument approaches. Participation is voluntary, and pilots may contact the approach control frequency.

Learning about and navigating SUAs as a student pilot was vital to the safety of my flight training. Certainly, I consistently relied on this knowledge. It served me well during my world flight, and it serves me today. Most importantly, understanding and experiencing the SUAs in the U.S. provided a solid foundation. This prepared me for my world flight thanks to the standardization efforts by IACO.

-Captain Judy Rice

Basic Dimensions and Requirements of Airspace Classes

Dimensions of Airspace Classes

What is Class A Airspace?

  • Extends from 18,000 feet (5,500 m) MSL to FL600.
  • Applies to contiguous United States and Alaska.
  • Flight levels depend on local atmospheric pressure variations.
  • ATC controls all flight operations, because this is controlled airspace.
  • Pilots must operate as IFR under a clearance received prior to entry.

What is Class B Airspace?

  • “B” is for “busy,” because Class B airspace is found around the busiest airports; for instance, New York and Atlanta.
  • Pilots must obtain ATC clearance prior to entry, because Class B is controlled airspace.
  • Aircraft must be equipped with a two-way radio
  • Also, aircraft must have an operating Mode C transponder, and automatic altitude reporting equipment.
  • Exact shape of the airspace varies from one class B area to another.
  • Usually shaped like an inverted wedding cake.
  • Has series of circular ‘shelves’ of airspace of several thousand feet in thickness, and each is larger than that beneath.
  • Centered on a specific airport.
  • Normally begins at the surface in the immediate area of the airport.
  • Successive shelves of increased radius begin at higher altitudes at greater distances from the airport.
  • Some flexibility to accommodate traffic patterns, local topology, etc.
  • Upper limit of class B airspace is normally 10,000 feet MSL.

What is Class C Airspace?

  • Similar to Class B, but on a smaller scale; for instance, Daytona Beach.
  • Pilots must establish two-way radio communication with ATC prior to entry. This is due to the fact that Class C is controlled airspace.
  • Aircraft must be equipped with a two-way radio and operating Mode C radar transponder.
  • Aircraft speed must be below 200 knots when at or below 2,500 feet above the ground, and within 4 nautical miles of the airport.
  • Typically at airports of moderate size/importance with regular commercial passenger jet service of 100 passengers per flight or more.
  • Operational control tower, radar-controlled approach system, and a minimum number of IFR approaches annually.
  • Airspace class designation is in effect only during the hours of tower and approach operation.
  • Airspace reverts to Class D if approach control is not operating, and to class E or G if the tower is closed.
  • Vertical boundary is usually 4,000 feet above the airport surface.
  • Core surface area radius is five nautical miles, and it extends from the surface to the ceiling.
  • The upper ‘shelf’ area radius is 10 nautical miles extending from as low as 1,200 feet up to the ceiling.

What is Class D Airspace?

  • Found at any airport with a functioning control tower, but with few IFR approaches.
  • Typically shaped like a cylinder extending from the surface to 2,500 feet above the ground.
  • Excludes airspace within the given radius, except in surrounding Class C or Class B airspace.
  • Reverts to Class E or G during hours when the tower is closed.
  • Establish two-way communication with ATC before entering, because it is controlled airspace.
  • No transponder is required.
  • VFR cloud clearance and visibility requirements are the same as Class C.

What is Class E Airspace?

  • Most airspace in the United States is class E.
  • No ATC clearance or radio communication required for VFR flight. However, Class E is controlled airspace.
  • VFR visibility and cloud clearance requirements are the same as for class C and D airspaces when below 10,000 feet MSL.
  • Above 10,000 feet MSL, visibility requirement extended to 5 miles.
  • Cloud clearance requirement extended to 1,000 feet below clouds, and 1,000 feet above, and 1 lateral mile.
  • Includes airspace above FL600.

What is Class F Airspace?

  • Not used in the U.S., due to special use areas.
  • In Canada, Class F is equivalent to special use airspace in the U.S.
  • IACO considers it a hybrid of Class E and Class G.

What is Class G Airspace?

  • Uncontrolled airspace, therefore no radio communication required.
  • All airspace below 14,500 feet MSL that is not otherwise classified as controlled.
  • No entry or clearance requirements, not even for IFR operations.
  • Typically this is the airspace very near the ground (1,200 feet or less). Furthermore, it is beneath Class E airspace, and between class B-D cylinders around towered airstrips.
  • VFR visibility requirements: 1 mile by day, 3 miles by night for altitudes below 10,000 feet but above 1,200 feet AGL.
  • 5 miles visibility required beginning at 10,000 feet MSL, day and night.
  • Cloud clearance requirements: maintain altitude 500 feet below, 1,000 feet above, 2,000 feet horizontal. At or above 10,000 feet MSL, 1,000 feet below, 1,000 feet above, and 1 mile laterally. By day, at 1,200 feet AGL, and below, remain clear of clouds, and no minimum lateral distance.

Due to obvious safety issues, pilots must understand all aspects of airspace classes, and they must comply. Most importantly, ICAO created airspace classes because of safety concerns. Consequently, air travel remains highly respected as a safe mode of travel. Furthermore, special circumstances arise that require temporary adjustments to airspace. When in doubt, find out. Above all, contact ATC if there is any question about your location and your right to be there. As a result, you will always find yourself in the right place at the right time!

Fun Fact Airspace

Did you know…?

Drones, or unmanned aircraft systems (UAM), must adhere to airspace rules, too. For instance, the FAA prohibits flying drones over rescue or emergency operations, such as hurricanes and wildfires. Small drones can only fly up to 400 feet AGL. If you are a drone operator, learn the rules. The FAA legally defines drones as aircraft. Therefore, you are accountable for knowing when and where you can safely fly your drone.

By Captain Judy Rice, Epic Ground School Instructor

Captain Judy Rice
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2 thoughts on “Airspace Classes”

  1. As always, awesome explanation in detail of Airspace Captain Judy!!

    It is a Privilege been an Epic’s Student having you as our Instructor on each lesson on the classroom!!


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