Drive through farmland in Europe or North America and you may pass something that looks like a landed flying saucer: a flat metal disc on stilts, ringed with small white domes, with a little hut underneath. It is not a radar and it is not listening to anyone. It is a VOR, and for more than seventy years it has been quietly telling every aircraft within range exactly which direction it lies from the station.

VOR stands for VHF omnidirectional range. It was the backbone of airway navigation from the late 1940s onward, and despite GPS it is still in use today. In the United States, the FAA is switching many stations off, but deliberately keeping a core network alive. Here is how VOR navigation works, why pilots trust it, and why it is not dead yet.

A lighthouse made of radio

The easiest way to picture a VOR is as a lighthouse with two lights. One is a flash that goes out in every direction at the same moment. The other is a beam that sweeps steadily around the compass. If you time the gap between the flash and the moment the beam passes you, you know your direction from the lighthouse.

A VOR does the same thing with two 30 Hz radio signals on a single VHF frequency between 108.0 and 117.95 MHz. One, the reference signal, is identical in every direction. The other, the variable signal, changes its phase depending on the direction it is radiated. The receiver in the aircraft compares the two, and the phase difference is the aircraft’s bearing from the station, measured from magnetic north.

That bearing is called a radial. A VOR offers 360 of them, one for each degree. An aircraft on the 090 radial is due east of the station, magnetically speaking, whichever way its nose is pointing. That is the key advantage over the older non-directional beacon: a VOR radial does not change with wind or with the aircraft’s heading.

Old and new stations

Early VORs created the rotating signal with a slightly directional antenna that spun, electrically, 30 times a second. Modern stations are usually Doppler VORs, or DVORs. They use a large circle of antennas, typically dozens of them, with no moving parts. The signal is switched around the ring electronically, and the Doppler effect of that apparent motion creates the bearing information. The ring is what gives a DVOR its flying-saucer look.

Every VOR also transmits a three-letter Morse code identifier, usually named after a nearby town or airport. That matters more than it sounds, because pilots must be sure they are tuned to the right station before trusting its needle.

Pilot and YouTuber Captain Joe explains what a VOR is and how pilots use it.

What the pilot sees

In a light aircraft, the classic VOR display is a round instrument with a knob called the omni bearing selector. The pilot dials in the course they want, and a vertical needle, the course deviation indicator, shows whether the aircraft is left or right of it. Keep the needle centred and you are on the radial.

A small TO/FROM flag resolves the obvious ambiguity: whether flying that course would take you towards the station or away from it. More advanced aircraft show the same information on a radio magnetic indicator or a horizontal situation indicator, which combines it with a heading card in a form much closer to a simple moving map.

The accuracy is the reason VORs built the airway system. Two radials from two different stations cross at a single point, giving a position fix. Lines from station to station became the airways, known in the United States as Victor airways below 18,000 feet and jet routes above it, and for decades instrument flying meant hopping from one VOR to the next.

Adding distance: DME and TACAN

A VOR tells you direction, not distance. For that, many stations are paired with distance measuring equipment, or DME. The aircraft sends out pairs of pulses, the ground station answers on a different frequency, and the aircraft times the round trip. According to the FAA, DME can work out to 199 nautical miles with an accuracy better than half a mile or 3 percent of the distance, whichever is greater. It measures slant range, so an aircraft directly over the station at 6,000 feet reads about one mile.

A radial plus a DME distance gives a position from a single station. Where the military is involved, VORs are often co-located with TACAN, the military system that provides both bearing and distance to military aircraft. The combined site is called a VORTAC. Afterburner explains the military side in TACAN Explained: How Military Jets Find Their Way Home.

Line of sight, and its limits

VHF radio travels in straight lines, so a VOR only works where the aircraft can, in effect, see the antenna. The FAA notes that range varies with the altitude of the receiving aircraft. That is the same physics that limits radar, explained in Radar Horizon: Why Flying Under the Radar Is Literal. A low-flying aircraft behind a hill can lose a station that a jet at cruising altitude receives clearly from far away.

Test and measurement company Rohde & Schwarz explains the principles of the VOR.

Switching off, but not all the way

Satellite navigation made much of the VOR network redundant. Under its VOR Minimum Operational Network programme, the FAA discontinued 82 VORs between fiscal years 2016 and 2020 and planned to discontinue 220 more between 2021 and 2030, according to an FAA briefing at Oshkosh in 2025. At that point, 200 had been switched off, and 594 VORs were planned for retention.

The survivors are not random. The FAA says the network will give nearly continuous VOR coverage at 5,000 feet above ground across the lower 48 states outside the western mountains, where the network is not being changed, and that a MON airport with an ILS or VOR approach will always be within 100 nautical miles. AOPA notes that all VORs in Alaska, the western mountainous area and the US islands and territories are being kept.

The reason is simple: GPS can fail or be jammed. Afterburner reported on one example in GPS Jamming Over Los Angeles. When satellites go quiet, a pilot can still tune a VOR, centre a needle and fly to a runway, exactly as pilots have done since the 1950s. The flying saucers in the fields are an insurance policy, and the FAA has decided it is one worth keeping.

Sources: FAA Aeronautical Information Manual (Chapter 1, Section 1), FAA VOR MON briefing (Oshkosh 2025), AOPA

Header photo: DKrieger / Wikimedia Commons, CC BY-SA 4.0