Airspace is the portion of theatmosphere controlled by acountry above its territory andterritorial waters that fall under the country's sovereignty and regulatory control.
Internationally, allocation and management of airspace is coordinated by theInternational Civil Aviation Organization (ICAO), which was established through the Chicago Convention in 1947 to unify air traffic. ICAO organizes airspace intoFlight Information Regions (FIRs) and provides classification guidelines. National authorities, such as theFAA,CAA, orEASA implement rules and regulations forair traffic control,special-use airspace, and enforcement within their own FIRs.
Airspace can be used for bothcivilian flight and for defense or military operations, and countries are responsible for protecting their own airspace using measures such asair policing. Legal and technical challenges include the vertical boundary between airspace and outer space and temporary restrictions such asNOTAMs orTFRs.
On 4 April 1947, theInternational Civil Aviation Organization (ICAO) was established through theChicago Convention, aimed at unifying and coordinating international air travel.[1] ICAO provides regulations and guidance for countries concerning air navigation, its infrastructure,flight inspection, prevention of unlawful interference, and facilitation of border-crossing procedures for internationalcivil aviation.[2]
Sovereign airspace refers to airspace owned by a country. By law, a country has the right to airspace above its land and waters up to 12 miles from their coast (if present). Beyond 12 miles, airspace is considered international.[3] ICAO divides airspace intoFlight Information Regions (FIR) which are sections of airspace dedicated to a specific country. A country is responsible, within its own FIR(s), to provide air traffic control services and regulation for flight.[4][5] This is usually done using a national regulator, such as theFAA,CAA, orEASA, which are able to create their own regulations while still abiding by ICAO guidelines.[6] Some countries may have multiple FIRs, for example, the United States has sole jurisdiction in 24 FIRs.[7] A country may, by international agreement, assume responsibility for providingair traffic control services in parts of international airspace, which then becomes part of their FIR.[8] Certain FIRs are dedicated oceanic sectors which support and control air traffic crossing large oceans such as theNorth Atlantic, which is made up of 7 FIRs controlled by countries like theUK,Ireland, andCanada.[9]
There is no international agreement on the vertical extent of sovereign airspace,[10] although most countries use theKármán Line, 100km (62mi), as the legal distinction between airspace and outer space.[11][12][13] However, descendingSpace Shuttles flew closer than 80 km (50 mi) over other nations, such as Canada, without requesting permission first.[14]
The boundary between public airspace and privateair rights is defined by national or local law.
In the United States, the 1946 Supreme Court decisionUnited States v. Causby overturned thecommon law doctrine that private property rights extend indefinitely upwards, instead ruling that they end 300 feet above the highest terrain (including buildings), the lower limit of the "public highway" defined by Congress in theAir Commerce Act of 1926. TheFederal Aviation Administration regulates the construction and marking of structures taller than 200 feet near airports and 500 feet generally.[15]
Airspace is divided into multiple classes which dictate what services are provided in different areas. The classes are defined by ICAO, but countries are free to allocate different sections of airspace to different classes as they wish. There are 7 classes, A-G, with progressively less strict restrictions. This classification system was adopted by ICAO on 12 March 1990.[16][17] Class F airspace is rarely used and is considered by ICAO to be a temporary measure before it can be replaced by an alternative classification.[18] For example, the CAA previous classified certain routes where air traffic control only provided an advisory service as Class F, before they were later reclassified as class E in 2014 after an official review.[19]
| Class | Permittedflight rules | Controlled | Separation provided | Services provided | Radio required | Requires ATC clearance to enter |
|---|---|---|---|---|---|---|
| A | OnlyIFR | Yes | All aircraft are separated from all others | Air traffic control service to all flights | Yes | Yes |
| B | IFR andVFR | Yes | All aircraft are separated from all others | Air traffic control service to all flights | Yes | Yes |
| C | IFR andVFR | Yes | IFR flights separated from all others. VFR flights receivetraffic information on IFR flights. | Air traffic control service to all flights | Yes | Yes |
| D | IFR andVFR | Yes | IFR flights separated from other IFR flights and receive traffic information on VFR flights. VFR flights receive traffic information on all other flights. | Air traffic control service to all flights | Yes | Yes |
| E | IFR andVFR | Yes | IFR flights separated from other IFR flights. | Air traffic control service to IFR flights, traffic information to all flights when practical | Yes | Yes for IFR, no for VFR |
| F | IFR andVFR | No | None provided | Participating IFR flights receive air traffic advisory service. Flight information service to all flights when practical (if available). | No | No |
| G | IFR andVFR | No | None provided | Flight information service to all flights when practical (if available). | No | No |
| [20] | ||||||
.svg)
Controlled airspace[21] exists where it is deemed necessary thatair traffic control has some form of positive executive control over aircraft flying in that airspace (however, air traffic control does not necessarily control traffic operating undervisual flight rules (VFR)[22] within this airspace). Controlled airspace consists ofclasses A-E.[17] Special types of controlled airspace, such as Control Zones (CTR) and Aerodrome Traffic Zones (ATZ) exist to protect aircraft in the vicinity of an airport, typically when arriving or departing.[23][24]
Uncontrolled airspace is airspace in which anair traffic control (ATC) service is not deemed necessary or cannot be provided for practical reasons. Uncontrolled airspace consists of classes F and G.[17] Aflight information service may still be provided to participating aircraft in some areas, depending on practicality and availability.[25]
Special use airspace (SUA) is airspace designated for operations that may cause limitations on other, uninvolved aircraft and exist to allow countries to separate certain areas of airspace that could be dangerous to flights within them. SUA may be controlled or uncontrolled, and does not have any specific classes associated with it.[26][27]
SUA includes:
Airspace may be temporarily restricted for safety. This may be via aNOTAM ortemporary flight restriction (TFR) for a variety of reasons, such as protecting major sporting events, natural disaster areas, air shows, or VIP movements.[28][29]
In the UK, airspace can be temporarily restricted by using a prohibited area, restricted area, or danger area—which designates areas where dangerous activities to flight may be taking place.[30][31]
.jpg)
In countries with an establishedmilitary, airspace is usually defended to protect national sovereignty. While military flights have to share airspace with civilians, they may usemilitary training routes or other special use airspace to protect civilian flights from dangerous activities.[32]
NATO conducts air policing missions to protect sovereign European airspace from both enemy military aircraft and civilian aircraft that fail to identify themselves, fail to communicate with air traffic control, or don't follow a flight plan.[33] They do this by keepingfighter aircraft in a 24/7 state ofquick reaction alert, ready to be scrambled at any time.[34]
For example, theRoyal Air Force maintains fourEurofighter Typhoons at 24/7 readiness: two atRAF Coningsby and two atRAF Lossiemouth.[34] Some NATO states do not have the capability to conduct QRA over their own territory, such as in the Baltic and Icelandic areas, so other NATO countries provide aircraft to cover instead.[35][36] In the United States, the quick reaction alert mission is referred to as Aerospace Control Alert, after having been renamed from Air Sovereignty Alert in 2011.[37] The majority of aerospace control alert missions in the U.S. are carried out by theAir National Guard using theF-15 Eagle andF-16 Fighting Falcon jets.[38][39]
Anair defense identification zone is a region of airspace where a country identifies, locates, and controls aircraft to protectnational security, which, in many cases, can cover airspace outside of the country's sovereign airspace.[40][41] A country may impose limitations on aircraft within them, such as requiring a flight plan to be filed.
In 2013,China established anADIZ in the East China Sea, drawing criticisms from neighbouring countries and the United States, as it overlaps existing zones and imposes requirements on both civilian and military aircraft.[42][43][44] Since 2010, China has been planning to establish an ADIZ over theSouth China Sea, which would raise tensions in theexisting territorial disputes. However, as of 2025, no ADIZ has been created.[45][46]
Russian aircraft are frequently tracked by theUnited States entering theirAlaska ADIZ,[47] often triggering QRA responses of American fighters.[48][49]
An airspace violation occurs when an aircraft enters controlled or national airspace without authorisation. Such incidents may be accidental, such as navigation or communication errors, or they may be deliberate, such as military reconnaissance or probing.[50]
In theCold War, aircraft such asKorean Air Lines Flight 007 were shot down due to misidentification as enemy military aircraft.[51] In 2023, a Chinese high altitudeballoon entered US airspace,[52] allegedly for intelligence gathering, and was subsequently shot down by an American jet, increasing tensions between the two countries.[53] In August and September 2025, Russiarepeatedly flew drones and aircraft intoNATO airspace, prompting NATO to launchOperation Eastern Sentry after anArticle 4 declaration.[54]
Performance-based navigation (PBN) is a type of navigation that allows aircraft to use GPS and other satellite navigation instead of only ground-based stations likeVORs which improves airspace safety, capacity, and efficiency.[55][56] ICAO and national authorities such as the FAA are gradually redesigning controlled and uncontrolled airspace to supportRequired Navigation Performance (RNP) andArea Navigation (RNAV) routes.[57] This changes allow for more efficient flight paths and reduce the need of maintaining specific physical sensors.[58] Projects led by service providers such asHughes Aerospace have demonstrated how PBN procedures can be used to optimize traffic flows and reduce noise in congested areas,[59] such as theNaples Municipal Airport in Florida.[60][61]
{{cite web}}: CS1 maint: multiple names: authors list (link)
| International | |
|---|---|
| National | |
| Other | |
