VOR, short for VHF omnidirectional radio range, is a type of radio navigation system for aircraft, enabling them to find their position and stay on course by receiving radio signals emitted by a network of radio beacons. It uses frequencies in very high frequency (VHF) from 108 to 117.95 MHz. Developed in the USA in 1937, VOR is the standard air navigational system in the world, used by both commercial and general aviation. There are about 3000 VOR stations around the world.