Editing VHF omnidirectional range (section)

===VORs, airways and the en route structure===
[[Image:VOR on sectional.gif|thumb|The Avenal VORTAC (at 35.646999,-119.978996) shown on a sectional aeronautical chart. Notice the light blue Victor Airways radiating from the VORTAC. (click to enlarge)]]
VOR and the older NDB stations were traditionally used as intersections along [[airway (aviation)|airways]]. A typical airway will hop from station to station in straight lines. When flying in a commercial [[airliner]], an observer will notice that the aircraft flies in straight lines occasionally broken by a turn to a new course. These turns are often made as the aircraft passes over a VOR station or at an intersection in the air defined by one or more VORs.
Navigational reference points can also be defined by the point at which two radials from different VOR stations intersect, or by a VOR radial and a DME distance. This is the basic form of [[RNAV]] and allows navigation to points located away from VOR stations. As RNAV systems have become more common, in particular those based on [[GPS]], more and more airways have been defined by such points, removing the need for some of the expensive ground-based VORs.

In many countries there are two separate systems of airway at lower and higher levels: the lower ''Airways'' (known in the US as ''Victor Airways'') and ''Upper Air Routes'' (known in the US as ''Jet routes'').

Most aircraft equipped for instrument flight (IFR) have at least two VOR receivers. As well as providing a backup to the primary receiver, the second receiver allows the pilot to easily follow a radial to or from one VOR station while watching the second receiver to see when a certain radial from another VOR station is crossed, allowing the aircraft's exact position at that moment to be determined, and giving the pilot the option of changing to the new radial if they wish.