Airspace class

The world's navigable airspace is divided into three-dimensional segments, each of which is assigned to a specific class. Most nations adhere to the classification specified by the International Civil Aviation Organization (ICAO) and described below, though they might use only some of the classes defined below, and significantly alter the exact rules and requirements. Similarly, individual nations may also designate Special Use Airspace with further rules for reasons of national security or safety.

ICAO definitions

On March 12, 1990, ICAO adopted the current airspace classification scheme.[1] The classes are fundamentally defined in terms of flight rules and interactions between aircraft and Air Traffic Control (ATC). Generally speaking, the ICAO airspaces allocate the responsibility for avoiding other aircraft, namely either to ATC (if separation is provided) or to the aircraft commander (if not).

Some key concepts are:

ICAO adopted classifications

Note: These are the ICAO definitions. Country-specific adaptations (such as "two-way communications" instead of "clearance" for Class C in the US) are discussed in the sections below.

Special Airspace: these may limit pilot operation is certain ares. Consist of Prohibited areas, Restricted areas, Warning Areas, MOAs (military operation areas), Alert areas, Controlled firing areas (CFAs) all on can be found on the flight charts.

Classes A–E are referred to as controlled airspace. Classes F and G are uncontrolled airspace.

The table below provides an overview of the above classes, and the specifications for each.

Class Controlled IFR SVFR VFR ATC Clearance Separation Traffic Information
A Controlled Yes No No Required Provided for all flights N/A
B Controlled Yes Yes Yes Required Provided for all flights N/A
C Controlled Yes Yes Yes Required Provided for all IFR/SVFR to IFR/SVFR/VFR Provided for all VFR
D Controlled Yes Yes Yes Required Provided for IFR/SVFR to other IFR/SVFR Provided for all IFR and VFR
E Controlled Yes Yes Yes Required for IFR and SVFR Provided for IFR/SVFR to other IFR/SVFR Provided for all IFR and VFR flights where possible
F Uncontrolled Yes No Yes advisory only Provided for IFR/SVFR to other IFR/SVFR where possible Provided where possible if requested
G Uncontrolled Yes No Yes Not provided Not provided Provided where possible if requested

Use of airspace classes

Each national aviation authority determines how it uses the ICAO classifications in its airspace design. In some countries, the rules are modified slightly to fit the airspace rules and air traffic services that existed before the ICAO standardisation.


Australia has adopted a civil airspace system based on the United States National Airspace System (NAS):

Transition from GAAP to Class D

Australia used to have a non-standard class of airspace for use at the capital city general aviation airports, called a General Aviation Airport Procedures Zone (GAAP Zone). A control tower provided procedural clearances for all aircraft inside the zone. Additionally, any aircraft operating within 5 nmi (9.3 km; 5.8 mi) of the zone must obtain a clearance. VFR aircraft arrive and depart using standard arrival and departure routes, while instrument arrival and departure procedures are published for IFR operations. During visual meteorological conditions (VMC), IFR aircraft are not provided with full IFR services. During instrument meteorological conditions (IMC), or marginal VMC, VFR operations are restricted in order to facilitate full IFR service for IFR aircraft.

As of the 3rd of June 2010, all GAAP aerodromes were changed to Class D aerodromes, and the previous Class D procedures were changed. The new Class D procedures are similar to the FAA Class D procedures. VFR Aircraft are no longer required to enter the airspace via set inbound/outbound points, however can be directed there by ATC. VFR and IFR aircraft now require taxi clearance in the "manoeuvring area" of the aerodrome, but can still taxi within set apron areas without a clearance. IFR aircraft now receive slot times and the visibility requirements of Special VFR are reduced from 3000m Visibility to 1600m.


Further information: Canadian airspace

There are seven classes of airspace in Canada, and each is designated by a letter (A through G).


In Estonia, airspace is divided into airspace class C and G only.


In Germany, Classes A and B are not used at all. Class C is used for Airspace above Flight Level (FL) 100 (or FL 130 near the Alps) up to FL 660. Airspace is divided into lower airspace below FL 245 and upper airspace above FL 245.


In Iraq, The Flight Information Regions (FIR) is known as Baghdad FIR. It is classified into Class A, D, E and G airspace. Class B, C and F airspace are not used in the Baghdad FIR. Air traffic services are provided in all controlled airspace, by the controlling ATC Unit, based on an ATS Surveillance System (supplemented by procedural non-ATS Surveillance System procedures) or MRU where authorized based on Procedural (non- ATC Surveillance System) procedures and supplemented by ATC Surveillance System where possible.



In Lithuania, Classes A and B are generally not used at all. Classes C and D are used in the following areas of controlled airspace of the Republic of Lithuania:


In the Netherlands, a relatively large part of the country is Class A airspace. Near Amsterdam, the capital of the Netherlands, the airspace is almost completely built up with class A. It starts at 1500' MSL, and ends at FL195. Further away from Amsterdam and its airport Schiphol, Class A starts at a higher altitude. Class B is used a lot as well. Anywhere in the Netherlands, Class A airspace ends at FL195 and changes in to Class C. Most of the CTRs are class D, some of them are class C. Class F is the only class that cannot be found in the Dutch airspace.


In Norway, airspace is divided into A, C, D and G.[3]


Classes A, C and G are used in Mauritius.[4]


Russia adopted a modified version of ICAO airspace classification on November 1, 2010. The division into classes for the airspace of the Russian Federation was introduced for the first time in the history of Russia.[5]

The airspace above the territory of the Russian Federation is divided as follows:

Airspace controlled by Russia outside the territory of Russia has different division into classes and includes redefined Class A and Class G, but no class C airspace.[6]

Specific boundaries of airspaces are determined by the Order of the Ministry of Transport of the Russian Federation #199 of September 15, 2010.[6][7]


In Sweden, airspace is divided into airspace class C and G only.

United Kingdom

Airways typically start at FL 70 and routing options become more attractive above FL 140.
Some airways & CTAs may have sections of Class C.

In addition the UK has a couple of special classes of airspace that do not fall within the ICAO classes:

United States

Airspace classes in the United States

The U.S. adopted a slightly modified version of the ICAO system on September 16, 1993, when regions of airspace designated according to older classifications were converted entirely. The exceptions are some Terminal Radar Service Areas (TRSA), which have special rules and still exist in a few places.

Airspace classes and VFR

Authorities use the ICAO definitions to derive additional rules for VFR cloud clearance, visibility, and equipment requirements.

For example, consider Class E airspace. It is possible that an aircraft operating under VFR is not in communication with ATC, so it is imperative that its pilot be able to see and avoid other aircraft (and vice versa). That includes IFR flights emerging from a cloud, so the VFR flight must keep a designated distance from the edges of clouds above, below, and laterally, and must maintain at least a designated visibility, to give the two aircraft time to observe and avoid each other. The low-level speed limit of 250 knots does not apply above 10,000 feet (3,000 m), so the visibility requirements are higher.

On the other hand, in Class B and Class C airspaces, separation is provided by ATC to all aircraft. Now the VFR pilot only needs to see where it is going, so visibility requirements are reduced and there is no designated minimum distance from clouds.

Similar considerations determine whether a VFR aircraft must use a two-way radio and/or a transponder.

Special use airspace

Each national authority designates areas of special use airspace (SUA), primarily for reasons of national security. This is not a separate classification from the ATC-based classes; each piece of SUA is contained in one or more zones of letter-classed airspace.

SUAs range in restrictiveness, from areas where flight is always prohibited except to authorized aircraft, to areas that are not charted but are used by military for potentially hazardous operations (in this case, the onus is on the military personnel to avoid conflict). Refer to the external links for more specific details.


  1. ICAO's airspace classification scheme is defined in ICAO Annex 11: Air Traffic Services, Chapter 2, Section 2.6., available at
  2. Airfield Guide Lithuania, 29 SEP 2005, ENR 1.1-1
  4. AIP Mauritius
  5. The Official Site of the Prime Minister of the Russian Federation, March 11, 2010.
  6. 1 2 3 4 5 Appendix to the Resolution of the Government of The Russian Federation #138 of March 11, 2010. (Russian)
  7. Order of the Ministry of Transport of the Russian Federation #199 of September 15, 2010. (Russian)
  9. Archived January 3, 2010, at the Wayback Machine.
  10. Godwin, Peter (1987–2004). The Air Pilot's Manual: Aviation Law And Meteorology. Cranfield, England: Air Pilot Publishing Ltd.
  11. FAA Order 7400.9, Subpart E
  12. "Pilot2Pilot - For Pilots by Pilots : Class B Airspace". Retrieved 2014-03-04.

External links

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