View source for Controlled airspace

{{Short description|Airspace served by air traffic control}}
{{distinguish|area control center}}
{{Use dmy dates|date=October 2021}}
{{Use Canadian English|date=October 2021}}
[[Image:Controlled_airspaces.png|thumb|Schematic representation of the main controlled airspace types and the air traffic control offices that respectively provide control service inside these airspaces.]]

'''Controlled airspace''' is [[airspace]] of defined dimensions within which [[air traffic control]] (ATC) services are provided.<ref>{{cite web |url=http://laws-lois.justice.gc.ca/eng/regulations/SOR-96-433/FullText.html#s-101.01 |title=Canadian Aviation Regulations (SOR/96-433) - Part I (General Provisions) - Subpart 1 (Interpretation) |publisher=Government of Canada |accessdate=2016-11-30 |url-status=live |archive-url=https://web.archive.org/web/20120403125803/http://laws-lois.justice.gc.ca:80/eng/regulations/SOR-96-433/FullText.html |archive-date=3 April 2012 }}</ref><ref>{{Cite web |title="PHAK Chapter 15" |url=https://www.faa.gov/sites/faa.gov/files/17_phak_ch15.pdf |url-status=live |access-date=28 September 2025 |website=FAA}}</ref><ref>{{Cite web |title=Controlled Airspace |url=https://infringements.caa.co.uk/tutorial/controlled-airspace/ |access-date=2025-09-28 |website=CAA Infringement Tutorial |language=en-GB}}</ref> The level of control varies with different [[airspace class|classes of airspace]]. Controlled airspace usually imposes higher weather minimums than are applicable in uncontrolled airspace.<ref>{{cite web |url=http://www.tc.gc.ca/eng/civilaviation/regserv/cars/part6-602-2436.htm#602_114 |title=Canadian Aviation Regulations - Part VI - Section 602.114 - General Operating and Flight Rules |publisher=[[Transport Canada]] |accessdate=2012-08-13 |archive-url=https://web.archive.org/web/20120919144314/http://www.tc.gc.ca/eng/civilaviation/regserv/cars/part6-602-2436.htm#602_114 |archive-date=2012-09-19 |url-status=dead }}</ref> It is the opposite of [[uncontrolled airspace]].

== Classes ==
The [[International Civil Aviation Organization]] divides airspace into seven classes, from [[airspace classes|A to G]], in order of decreasing ATC regulation of flights. Classes A to E are considered controlled airspace. Flight under [[instrument flight rules]] (IFR) is allowed in all controlled airspace, and flight under [[visual flight rules]] (VFR) is permitted in all airspace except class A.<ref>{{cite web |date=2012-04-11 |title=TP 14371 - Transport Canada Aeronautical Information Manual (TC AIM) - RAC - 2.0 AIRSPACE – REQUIREMENTS AND PROCEDURES |url=http://www.tc.gc.ca/eng/civilaviation/publications/tp14371-rac-2-0-2599.htm#2-5 |url-status=dead |archive-url=https://web.archive.org/web/20110218033451/http://www.tc.gc.ca/eng/civilaviation/publications/tp14371-rac-2-0-2599.htm#2-5 |archive-date=2011-02-18 |accessdate=2012-08-13 |publisher=[[Transport Canada]]}}</ref><ref>{{Cite web |title=Classification of Airspace {{!}} SKYbrary Aviation Safety |url=https://skybrary.aero/articles/classification-airspace |access-date=2025-09-28 |website=skybrary.aero}}</ref>
{| class="wikitable"
|+
!Name
!Permitted [[Flight rules (disambiguation)|flight rules]]
!Separation provided
!Services provided
!Radio required
!Requires ATC clearance to enter
|-
|Class A
|Only [[Instrument flight rules|IFR]]
|All aircraft are separated from all others
|Air traffic control service to all flights
|{{yes}}
|{{yes}}
|-
|Class B
|[[Instrument flight rules|IFR]] and [[Visual flight rules|VFR]]
|All aircraft are separated from all others
|Air traffic control service to all flights
|{{yes}}
|{{yes}}
|-
|Clas C
|[[Instrument flight rules|IFR]] and [[Visual flight rules|VFR]]
|[[Instrument flight rules|IFR]] flights separated from all others. VFR flights receive traffic information on IFR flights.
|Air traffic control service to all flights
|{{yes}}
|{{yes}}
|-
|Class D
|[[Instrument flight rules|IFR]] and [[Visual flight rules|VFR]]
|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}}
|-
|Class E
|[[Instrument flight rules|IFR]] and [[Visual flight rules|VFR]]
|IFR flights separated from other IFR flights. All flights may receive traffic information when practical.
|Air traffic control service to IFR flights, traffic information to VFR flights when practical
|{{yes}}
|{{maybe|Yes for IFR, no for VFR}}
|-
| colspan="6" |<ref>{{Cite web |title=Classification of Airspace {{!}} SKYbrary Aviation Safety |url=https://skybrary.aero/articles/classification-airspace |access-date=2025-09-28 |website=skybrary.aero}}</ref>
|}

== Types ==
Certain special types of controlled airspace exist to protect aircraft in the vicinity of a busy [[airport]].

=== Control Zone (CTR) ===
{{More citations needed|section|date=September 2025}}
A '''control zone''' is a volume of controlled airspace, normally around an [[airport]], which extends from the ''surface'' to a ''specified upper limit'', established to protect air traffic operating to and from that airport. Because CTRs are by definition controlled airspace, aircraft can only fly in them after receiving a specific clearance from [[air traffic control]]. This means that air traffic control at the airport know exactly which aircraft are in that airspace, and can take steps to ensure aircraft are aware of each other, either using separation or by passing traffic information.

A CTR requires permanent radio contact while being in it, and a clearance before entering. Certain activities such as making an approach, landing and taking off also require clearances. This implies that an aircraft flying in it must be equipped with a radio. There are procedures for radio failures.

In the USA the term control zone is no longer used<ref>[[FAA]]: [https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/17_phak_ch15.pdf]</ref> and has been replaced by [[Airspace_class_(United_States)#Class_D|airspace class D]]. Typically it extends 5 miles in diameter with a height of 2500&nbsp;ft AGL (above ground level) around small commercial airports.

In the UK, control zones are normally class D airspace and usually extend from the surface to 2000&nbsp;ft AGL. They can be observed to be usually rectangular, extending along the axis of the main runway, although irregular shapes may be used where more complex airspace dictates this (see Liverpool and East Midlands). A control area (CTA) is often placed between a CTR and nearby airways to give uninterrupted controlled airspace to airways arrivals and departures.

In Germany, control zones are a special type of class D airspace, called ''D (CTR)''. The main difference to the regular German class D airspace is, that within a CTR there is a minimum required cloud ceiling of 1500&nbsp;ft AGL.<ref>[[Deutsche Flugsicherung]]: [https://www.dfs.de/dfs_homepage/de/Flugsicherung/Luftraum/luftraumstruktur_092016.pdf Airspace Structure/Visual Flight Rules in the Federal Republic of Germany – Example] {{Webarchive|url=https://web.archive.org/web/20181224023757/https://www.dfs.de/dfs_homepage/de/Flugsicherung/Luftraum/luftraumstruktur_092016.pdf|date=2018-12-24}}</ref>

=== Control area (CTA) ===
A '''control area''' is a section of controlled airspace that extends upwards from a specified limit above the earth, which must be above 200m (700ft),<ref name="Annex11">{{cite web |date=July 2018 |title=Annex 11 to the Convention on International Civil Aviation: Air Traffic Services |url=https://ffac.ch/wp-content/uploads/2020/10/ICAO-Annex-11-Air-Traffic-Services.pdf |access-date=2024-06-28 |publisher=International Civil Aviation Organization (ICAO) |edition=15}}</ref> and are established in areas where the density of traffic is high. The upper limit of a control area is either when an air traffic control service will not be provided above, or there is another control area above.<ref name="Smith">{{Cite book |last=Smith |first=David |title=Air Traffic Control Handbook |date=2021 |publisher=Crécy Publishing Ltd |isbn=978-1-9108-0999-0 |location=[[Manchester]], England}}</ref>

A control area usually is situated on top of a control zone (CTR) and provides protection to aircraft climbing out from the airport by joining the low-level control zone to the nearest airways. In the UK, they are generally class A, D or E.<ref>{{Cite web |title=Understanding airspace {{!}} UK Civil Aviation Authority |url=https://www.caa.co.uk/commercial-industry/airspace/airspace-change/understanding-airspace/ |access-date=2025-09-08 |website=www.caa.co.uk}}</ref>

A '''terminal control area (TMA)''' is a control area established surrounding one or major airports at the confluence of airways. It typically sits above each individual airport's CTR.<ref>{{Cite web |title=Terminal Control Area (TMA) {{!}} SKYbrary Aviation Safety |url=https://skybrary.aero/articles/terminal-control-area-tma |access-date=2025-09-08 |website=skybrary.aero}}</ref>

=== Terminal radar service area (TRSA) ===
In the [[United States]], a '''terminal radar service area''' is a section of airspace surrounding a busy airport where optional [[air traffic control]] services are provided. It is designated as [[Airspace class|Class E]] airspace.<ref>{{Cite web |last=Institute |first=Pilot |date=2025-02-01 |title=TRSA Airspace Explained (Terminal Radar Service Area) |url=https://pilotinstitute.com/trsa-airspace-explained/ |access-date=2025-09-28 |website=Pilot Institute |language=en-US}}</ref>

=== Aerodrome Traffic Zone (ATZ) ===
An '''aerodrome traffic zone''' is a small section of airspace defined around an aerodrome to protect the traffic departing or arriving. The dimensions vary. In the UK, it is typically defined as:<ref>{{Cite web |title=Aerodrome Traffic Zone (ATZ) {{!}} SKYbrary Aviation Safety |url=https://skybrary.aero/articles/aerodrome-traffic-zone-atz |access-date=2025-09-28 |website=skybrary.aero}}</ref>

* Extending from the surface to 2000ft and with a radius of 2.5NM around the longest runway when the longest runway is longer than 1850m
* Extending from the surface to 2000ft and with a radius of 2.0NM around the longest runway when the longest runway is shorter than 1850m

==See also==
*[[Airspace class]]
*[[Prohibited airspace]]
*[[Restricted airspace]]
*[[Special use airspace]]
*[[Terminal control area]]

==References==
{{reflist}}

{{Commercial air travel}}

[[Category:Air traffic control]]


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