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Navigation Programs — VOR MON

What is the VOR MON?

VOR - Very High Frequency Omni-directional Range
The Very High Frequency Omni-directional Range (VOR) Minimum Operational Network (MON) provides a conventional navigation backup service in the event of a loss of Global Positioning System (GPS) signal.

The VOR MON includes the minimum number of FAA owned VORs geographically situated in the contiguous United States (CONUS) necessary to provide coverage at and above 5,000 feet above ground level (AGL), support approaches to MON airports and meet other criteria.


On December 15, 2011, the FAA published in the Federal Register a notice of proposed policy and request for comments (76 FR 77939) on the FAA's proposed strategy for gradually reducing the FAA owned VOR network in the CONUS to a MON. This strategy supports the National Airspace System (NAS) transition from VOR navigation to Performance Based Navigation (PBN) consistent with NAS modernization goals.

The FAA reviewed all comments received and on August 21, 2012, published in the Federal Register the disposition of the comments on the notice of proposed policy (77 FR 50420).

After the FAA published the disposition of comments, stakeholders, industry, and military services provided further inputs to the FAA for consideration. The FAA also sought recommendations from aviation industry stakeholders through the RTCA Tactical Operations Committee (TOC).

On July 26, 2016, the FAA published (81 FR 48694) Provision of Navigation Services for the Next Generation Air Transportation System (NextGen) Transition to Performance-Based Navigation (PBN) (Plan for Establishing a VOR Minimum Operational Network).

Concepts of Operations

The FAA continues to plan the NAS transition from defining Air Traffic Services (ATS) routes and instrument procedures using VORs and other conventional NAVAIDs to a point-to-point system based on Area Navigation (RNAV) and Required Navigation Performance (RNP). RNAV will generally be available throughout the NAS and RNP will be provided where beneficial. The FAA's network of Distance Measuring Equipment (DME) NAVAIDs will provide a PBN-capable backup to GPS; however, for aircraft without scanning DME receivers (DD) or DD with Inertial Reference Unit aiding (DDI) equipment, the FAA will provide a conventional navigation backup service based on the VOR MON. The VOR MON is designed to enable aircraft, having lost GPS service, to revert to conventional navigation procedures. This would allow users to continue through the outage area using VOR station-to-station navigation or to proceed to a MON airport where an Instrument Landing System (ILS), Localizer (LOC) or VOR approach procedure can be flown without the necessity of GPS, DME, Automatic Direction Finder (ADF), or surveillance. Of course, any airport with a suitable instrument approach may be used for landing, but the VOR MON assures that at least one airport will be within 100 NM.

In order to enable VOR station-to-station navigation, two new geometrically larger VOR Standard Service Volumes (SSVs) are being implemented to provide VOR signal starting at 5,000 feet Above Ground Level (AGL). Coverage will exist but may not be continuous at lower altitudes.

The new geometrically larger SSVs allow reduction of the VOR network in CONUS. No changes to the equipment were necessary to implement the new SSVs.

For more details on how to use the VOR MON, we have included below the applicable link for the Aeronautical Information Manual (AIM).

The VOR MON Program timeline. The timeline begins in fiscal year 2016 with 896 VORs and ends in fiscal year 2030 with 589 VORs.
The VOR MON Program timeline. (Click for larger view)

FAA Contact: Leonixa Salcedo, VOR MON Program Manager
Tel.: (844) 4-VORMON; (844) 486-7666

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