Omega (navigation System)
OMEGA was the first truly global radio navigation system for aircraft, operated by the United States in cooperation with six partner nations. It enabled ships and aircraft to determine their position by receiving very low frequency (VLF) radio signals transmitted by a network of fixed terrestrial radio beacons, using a receiver unit. It became operational around 1971 and was shut down in 1997.
Read more about Omega (navigation System): Court Case, OMEGA Test Locations