Airway (aviation)
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In aviation, an airway is a designated route in the air. Airways are laid out between navigation aids such as VORs, NDBs and Intersections (NDB-based airways are rare in the United States, but are more common in much of the rest of the world).
In the United States low altitude airways (below 18,000 feet [5,500 m] MSL), appear on sectional world aeronautical charts and enroute low altitude charts and are designated by the letter "V" (pronounced Victor, hence Victor airways). High altitude airways (above 18,000 ft [5,500 m] MSL), called jet routes, appear on high altitude charts (that usually don't show topography, as the low altitude charts do) and are designated by the letter "J".
In the United States, Victor airways are Class E airspace from 1,200 ft above ground level (AGL) to 18,000 ft MSL (Mean Sea Level). The width of the victor corridor depends on the distance from the navigational aids (such as VOR's and NDB's). When VOR's are less than 102NM from each other, the Victor airway extends 4NM on either side of the center line (8nm total width). When VOR's are more than 102NM from each other, the width of the airway in the middle increases. The width of the airway beyond 51NM from a navaid is 4.5 degrees on either side of the center line between the two navaids (at 51NM from a navaid, 4.5 degrees from the centerline of a radial is equivalent to 4NM). The maximum width of the airway is at the middle point between the two navaids. This is when 4.5 degrees from the center radial results in a maximum distance for both navaids.
In Europe, airways are corridors 10 nautical miles (19 km) wide of controlled airspace with a defined lower base, extending to FL195. They link the major airports giving protection to IFR flights during the climb and descent phases, and often for non-jet aircraft, cruise phases of flight. Historically they were laid out between VORs, however advances in navigational technology mean that nowadays this is not always the case. Like roads, 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 a U. If an upper air route follows the same track as an airway its designator will be identical to the airway, prefixed with a U.
