View source for Airway (aviation)

[[File:IFR Chart.png|thumb|right|375px|IFR aeronautical charts depict VOR airways (airways based on VOR or VORTAC NAVAIDs) in black, identified by a "V" (Victor) followed by the route number (e.g., V12).]]

In the United States, '''airways'''<ref>{{cite book |title=A Dictionary of Aviation |first=David W. |last=Wragg |isbn=9780850451634 |edition=first |publisher=Osprey |year=1973 |page=31}}</ref> or '''air routes''' are defined by the [[Federal Aviation Administration|Federal Aviation Administration (FAA)]] in two ways:

"VOR Federal airways and Low/Medium Frequency (L/MF) (Colored) Federal airways"<ref>{{Cite web|title=Air Traffic Service Routes - Section 3. Federal Airways|url=https://www.faa.gov/air_traffic/publications/atpubs/pham_html/chap20_section_3.html|url-status=live|archive-url=https://web.archive.org/web/20201019203750/https://www.faa.gov/air_traffic/publications/atpubs/pham_html/chap20_section_3.html |archive-date=2020-10-19 }}</ref>

These are designated routes which [[aeroplane]]s fly to aid in navigation and help with separation to avoid accidents.<ref>{{cite book|last=Gunston|first=Bill|title=The Cambridge Aerospace Dictionary Cambridge|url=https://archive.org/details/cambridgeaerospa00guns|url-access=limited|publisher=Cambridge University Press|year=2004|isbn=978-0521841405|pages=[https://archive.org/details/cambridgeaerospa00guns/page/n43 34]}}</ref><ref>[https://web.archive.org/web/20120309151642/http://www.faa.gov/air_traffic/publications/atpubs/aim/aim0503.html FAA regulations 5-3-4. Airways and Route Systems] in Section 3. En Route Procedures; archived from ''www.faa.gov'', accessed 25 October 2020</ref><ref>[http://www.skybrary.aero/index.php/Airway Airway (definition)- Airway Description] ''www.skybrary.aero'', accessed 25 October 2020</ref>{{efn|The term ''airway'' is used by aviation professionals including the [[International Civil Aviation Organization]] (ICAO), but other terms have been used or misused by non-specialist sources, sometimes to mean the same thing.}} Airways are defined with segments within a specific altitude block, corridor width, and between fixed geographic coordinates for [[Satellite navigation system|satellites navigation system]], or between ground-based [[radio transmitter]] [[navigational aid]]s (navaids; such as [[VHF omnidirectional range|VOR]]s or [[Non-directional beacon|NDB]]s) or the [[Intersection (aviation)|intersection]] of specific radials of two navaids.

==United States==

=== History ===
To guide airmail pilots on their delivery routes, the [[United States Postal Service]] constructed the first airways in the United States, the [[Airmails of the United States#Beginning Contract Air Mail (CAM) service|Contract Air Mail routes]]. These airways were between major cities and identified at night by a series of flashing lights and beacons which pilots flew over in sequence to get from one city to the next.<ref>{{cite book|title=Pilot's Handbook of Aeronautical Knowledge|url=https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/pilot_handbook.pdf#page=21|publisher=U.S. Department of Transportation: Federal Aviation Administration|date=2016|page=1‑4|access-date=2021-04-12}}</ref> Intermediate fields were located every {{convert|30|mi|km}} in case of emergencies, with at least two landing strips a minimum of {{convert|2000|ft|m}} in length, and {{convert|600|ft|m}} in width. Rotating airways beacons were erected every {{convert|10|mi|km}}.<ref name="fs">{{cite book |last1=Smith |first1=Frank |title=Legacy of Wings; The Harold F. Pitcairn Story |date=1981 |publisher=Jason Aronson, Inc. |location=New York |isbn=0876684851 |page=97}}</ref> However, these visual airways required the pilots to be in visual contact with the ground, which precluded flying in fog or clouds. Subsequently, the Department of Commerce funded the development of other means of airway navigation.<ref>{{cite web|url=http://www.centennialofflight.net/essay/Government_Role/navigation/POL13.htm |title=The Evolution of Airway Lights and Electronic Navigation Aids |publisher=Centennialofflight.net |date=1924-07-01 |access-date=2014-07-28}}</ref>

The first airways to be delineated by radio frequency were based on the old [[Low-frequency radio range]] also called the "Four Course Radio Range" or "A/N" system. The pilot listened for the stronger of the Morse codes transmitters ("· –" for "A" and "– ·" for "N", indicating left or right of the course); the objective was to be centered on course hearing a steady tone (the A and N Morse codes merge to form a steady tone when the receiver is equidistant from both transmitters).

Later airways were based on low/medium frequency ground stations, like the [[beat frequency oscillator]] (BFO) and the [[non-directional beacon]] (NDB). These L/M frequency airways were the ''colored airways''. Colored airways still exist, mostly in Alaska. There are only a few colored airways remaining in the contiguous United States. There is one colored airway on the coast of North Carolina called G13 (Green 13). There is one Canadian colored airway designated A16 (Amber 16) that transits through US airspace in northwestern [[Washington (state)|Washington State]] and is visible on the Seattle [[Aeronautical Chart|sectional chart]]. Additionally, there are several colored airways connecting to, and transitioning through, the Florida Keys. B9 (Blue 9) connects the Southern Florida mainland to Marathon Key. B646 (Blue 646) connects Mérida, Mexico to [[Nassau, Bahamas]] and transitions through the Florida Keys. A portion of B646 connects Key West to Marathon Key and serves as a bypass for aircraft unable to meet the 15,000 foot minimum altitude along that portion of V3. Finally, G765 (Green 765) connects Key West to Cozumel, Mexico. Colored airways are all depicted in brown on low and high altitude charts produced by the [[Federal Aviation Administration|FAA]]'s Aeronautical Navigation Products.

=== Boundary ===
Federal airways is defined to be {{cvt|8|nmi}} wide and usually a floor of {{cvt|1,200|ft}} above the ground. It does not include the airspace of a prohibited area.<ref name="IFH">{{cite book |title=Instrument Flying Handbook |publisher=[[Federal Aviation Administration]] |edition=FAA-H-8083-15B |url=https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/FAA-H-8083-15B.pdf |year=2012 |chapter=Chapter 1: The National Airspace System |pages=4–5}}</ref> [[Aerobatics|Aerobatic flights]] are prohibited within federal airways.<ref>{{cite web |title=14 CFR 91.303. Aerobatic flight |url=https://www.ecfr.gov/current/title-14/section-91.303 |website=[[National Archives and Records Administration|National Archives]] |access-date=30 December 2024}}</ref>

=== Victor airways  ===
Low altitude airways (below {{convert|18000|ft|m}} [[Mean Sea Level|MSL]]) that are based on VOR stations, appear on sectional charts, world aeronautical charts, and en route low altitude charts and are designated with the prefix "V" (pronounced ''victor'', hence, ''[[victor airways]]''). Victor airways are usually assigned odd route numbers for north-south routes and even route numbers for east-west routes. Route numbers are listed serially if more than one airways share the same route segment.<ref name="IFH" />

=== Jet routes ===
High altitude airways (from {{convert|18000|ft|m}} MSL to [[Flight level|FL450]]) based on VOR stations are called [[Jet aircraft|jet]] routes; they appear on high altitude charts (that usually do not show topography, as the low altitude charts do) and are prefixed by the letter "J". VOR-based routes are depicted in black on low and high altitude charts produced by the FAA's Aeronautical Navigation Products.<ref name="IFH" />

=== RNAV routes ===
With the invention of [[Area navigation|RNAV]] routes, airway structure no longer has to be based on ground-based navaids; a new naming convention is used. RNAV routes not based on VOR routes in low altitudes are preceded with the letter "T"; high airway routes are designated with the letter "Q". RNAV routes are depicted in blue on low and high altitude charts produced by the FAA's Aeronautical Navigation Products. In addition to the published RNAV routes, if radar monitoring and traffic flow allow, air traffic controllers may approve random RNAV routes for IFR flights.<ref name="IFH" />

==Europe==

Airways are corridors {{convert|10|nmi|km}} wide of [[controlled airspace]] with a defined lower base, usually [[Flight level|FL070–FL100]], extending to FL195.  They link major airports giving protection to [[instrument flight rules|IFR]] flights during the climb and descent phases, and often for non-jet aircraft, cruise phase of flight.  Historically, they were laid out between [[VHF omnidirectional range|VOR]]s; however, advances in navigational technology mean that this is no longer a necessity.  Each airway has a designator containing one letter and one to three numbers.  All airspace above FL195 is class C controlled airspace, the equivalent to airways being called Upper Air Routes and having designators prefixed with the letter "U".  If an upper air route follows the same track as an airway, its designator is the letter "U" prefix and the designator of the underlying airway.

In the UK, airways are all class A below FL195 and, therefore, [[Visual flight rules|VFR]] flights are prohibited.

==Air corridor==
An air corridor is a designated region of [[airspace]] that an aircraft must remain in during its transit through a given region.  Air corridors are typically imposed by military or diplomatic requirements. During the [[Berlin Blockade]], for example, pilots flying across Soviet-controlled [[Germany|German]] airspace were required to maintain very specific positioning within [[West Berlin Air Corridor|air corridor]]s defined by the commander in charge of the airlift. Subsequent flights, both military and civilian, between [[West Germany]] and [[West Berlin]] during the [[Cold War]] were required to remain within their designated corridor or risk being shot down.

Air corridors should not be confused with airways. Airways are navigational aids which a pilot generally may deviate from when circumstances warrant, while compliance with a designated air corridor is mandatory.

==External links==
* [https://www.faa.gov/documentLibrary/media/Order/7400.2L_Bsc_w_Chg1_dtd_10-12-17.pdf FAA Order JO 7400.2L, Procedures for Handling Airspace Matters], effective 2017-10-12 (with changes), accessed 2017-12-04
* [https://web.archive.org/web/20090712031134/http://www.faa.gov/air_traffic/publications/ATpubs/AIM/ FAA Aeronautical Information Manual, Chapter 1]
* [http://www.berlin1969.com/stories-geschichte/troubled-times-unruhige-zeiten/air-corridor-pawns/ Cold War Berlin air corridor disagreement.]
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[[Category:Airway (aviation)]]
[[Category:Air Traffic Routes]]
[[Category:Instrument Flight Rules]]
[[Category:VOR Airways]]
[[Category:RNAV Routes]]
[[Category:Flight Planning]]
[[Category:Enroute Navigation]]
[[Category:Controlled Airspace]]
[[Category:Upper Airspace]]
[[Category:Air Traffic Services]]
[[Category:ATC Procedures]]
[[Category:Navigation Waypoints]]
[[Category:Air Route Traffic Control Centers]]
[[Category:Enroute Charts]]
[[Category:Aeronautical Information Publications]]
[[Category:Navigation Aids]]
[[Category:Area Navigation]]
[[Category:High Altitude Airways]]
[[Category:Low Altitude Airways]]
[[Category:Jet Routes]]
[[Category:Standard Instrument Departures]]
[[Category:Standard Terminal Arrivals]]
[[Category:Flight Management Systems]]
[[Category:ATC Communication]]
[[Category:Aeronautical Navigation Systems]]
[[Category:Global Air Navigation]]
[[Category:IFR Navigation]]
[[Category:Waypoint Coordination]]
[[Category:International Airspace]]
[[Category:Aviation Navigation Infrastructure]]
[[Category:Aviation Route Planning]]
[[Category:ATS Route Designators]]
[[Category:Navigation Infrastructure]]
[[Category:Flight Corridor Management]]
[[Category:Aviation Route Networks]]
[[Category:Airspace Classification]]
[[Category:Aviation Waypoint Management]]
[[Category:ATC Airspace Sectors]]
[[Category:Enroute Traffic Flow]]
[[Category:Navigation Route Safety]]
[[Category:Flight Level Allocation]]
[[Category:Flight Route Safety]]
[[Category:Navigation Data Integrity]]
[[Category:Enroute Safety Protocols]]
[[Category:Air Route Optimization]]
[[Category:Waypoint Database Systems]]
[[Category:Long Range Navigation]]
[[Category:Navigation Procedures]]
[[Category:ATC Clearance Procedures]]
[[Category:Aviation Route Mapping]]
[[Category:Flight Routing Constraints]]
[[Category:Aviation Safety X]]
[[Category:ASXWiki]]