Airport Classes Defined

Airports · 5 min read · Jul 22, 2022
airport classes

There are many different airports around the world. Some of them are huge while others are so small that most people do not even know about them. According to the Federal Aviation Administration (FAA), “there are approximately 14,400 private-use (closed to the public) and 5,000 public-use (open to the public) airports, heliports, and seaplane bases” in the United States. Clearly, with such a large number of airports there are a lot of different classes of them.

Keeping this in mind, let’s take a look at the different airport classes and what type of aircraft run operations in each class.

What are the different classes of airports?

Airport classes follow the FAA Part 139 where classes are determined according to the type of air carrier operations served. As we mentioned before, some airports can take large aircraft operations, and they should be certified under Part 139 to do so.

FAA Part 139 airport classes include class I, class II, class III, and class IV.

Airport Class I

Based on the FAA Part 139, airports certified as Class I are those serving all types of scheduled operations of air carrier aircraft designed for at least 31 passenger seats which are considered large air carrier aircraft. Also, the FAA states that Class I airports can serve any other type of air carrier operations. In other words, this is the most comprehensive of the classes. Larger airports tend to belong to Class I.

Airport Class II

Class II refers to all airports serving scheduled operations of small air carrier aircraft and unscheduled operations of large air carrier aircraft. Based on FAA Part 139, Class II airports are not permitted to serve scheduled large air carrier operations.

An aircraft being pushed down the taxiway of a class I airport.

Airport Class III

Airports falling in the Class III group only serve scheduled operations of small air carrier aircraft. While certification requirements apply to this class, some airports in Alaska are exempt from these requirements.

Airport Class IV

The final airport class according to Part 139 refers to airports that serve only unscheduled operations of large air carrier aircraft. Air carrier operations do not take place regularly at these airports, but they must still comply with certain requirements.

Part 139 Operational and Safety Requirements

All airports must meet certain operational and safety requirements to be certified to the corresponding class according to the FAA Part 139. While there are common requirements across the airport classes, each class may have specific requirements as well as exceptions based on the operations they serve.

For example, all classes are required a recordkeeping system and new personnel training per § 139.303. More information on the operational and safety requirements per Part 139 and the most recent revisions can be found here.

Airports and airspace classes

Airports can also be classified by using other categories apart from the classes mentioned above. In fact, the FAA has another classification which is based on the airport operation and activity, and it has three categories:

  • Commercial service
  • Reliever
  • General aviation

From the list above, commercial service airports refer to those “publicly owned airports with at least 2,500 annual enplanements and scheduled air carrier service” which include the following subcategories:

  • Large hub
  • Medium hub
  • Small hub
  • Nonhub
  • Nonprimary Commercial Service, Nonhub

Also, other categories are created based on the population of the location and the role of the airport in the system. However, a more interesting classification is the one that relates to airspaces.

An aircraft flying through a class A airspace during daytime.

What are airspaces?

Airspaces are defined as volumetric sections of the air where certain flying rules apply and they are classified according to the International Civil Aviation Organization (ICAO) to facilitate air transport regulations.

What are the 6 classes of airspace?

According to ICAO, there are actually 7 classes of airspace named with letters from A through G. However, class F is not used in the United States, which is why many people believe there are only 6. The 7 classes are as follows:

Class A

Only IFR flights are permitted, all flights are provided with ATC service and are separated from each other.

Class B

IFR and VFR flights are permitted, all flights are provided with ATC service and are separated from each other.

Class C

IFR and VFR flights are permitted, all flights are provided with ATC service and IFR flights are separated from other IFR flights and from VFR flights. VFR flights are separated from IFR flights and receive traffic information in respect of other VFR flights.

Class D

IFR and VFR flights are permitted and all flights are provided with ATC service, IFR flights are separated from other IFR flights and receive traffic information in respect of VFR flights, VFR flights receive traffic information in respect of all other flights.

Class E

IFR and VFR flights are permitted, IFR flights are provided with ATC service and are separated from other IFR flights. All flights receive traffic information as far as it is practical. Class E shall not be used for control zones.

Class F

IFR and VFR flights are permitted, all participating IFR flights receive an air traffic advisory service and all flights receive flight information service if requested.

Class G

IFR and VFR flights are permitted and receive flight information service if requested.

Tokyo Haneda airport waiting hall and an aircraft parked at a jetway on a clear day.

What are B, C, and D airport classes?

There are three classes of airports that follow the airspace classification described above. They are class B, class C, and class D airport. Let’s see what these categories involve.

What is a Class B airport?

Large airports such as those in New York, Chicago, and Los Angeles with a high volume of traffic which operate under strict ATC control. The airspace is composed generally of three concentric tiers. A core area around the airport is generally surrounded by two additional shelf areas extending approximately a 30 nautical mile radius from the primary airport.

What is a Class C airport?

Airports located in Class C airspace zones. These zones are designed for the enhancement and control of air traffic operations within the terminals, and the reduction of the risk of mid-flight collisions. Aircraft operating in this area must meet certain equipment requirements and operating regulations. Class C airspace has two concentric tiers. The inner circle is a 5 nautical mile core area extending to 4000 feet above the surface. It is similar in function to Class D airspace where the tower usually maintains jurisdiction.

What is a Class D airport?

These are airports that have a control tower but a low volume of traffic. The control tower has jurisdiction within the Class D airspace which is 5 statute miles radius around the control tower. The top of the airspace extends 2500 feet above the surface of the airport. Two-way radio contact must be maintained with the Control Tower while in this airspace. The pilot should contact the control tower prior to entering the airspace.

Some final words

As you can see, there is a large volume of airports around the world and there are many different aspects that are being used in classifying airports. Classification of airports is vital for the safety of all grounded and airborne flights as tight monitoring and control prevent accidents and incidents. Of course, as a rule in aviation, the most important requirement for safety is still following rules and offering clear communication.

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Carlos Collantes
Carlos Collantes
A mechanical engineer and aviation enthusiast dedicated to share some knowledge by creating top-notch content, especially in engineering and aviation topics.

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