Which NAVAID is considered the primary navigation aid for the National Airspace System (NAS)?

The VOR, or VHF Omnidirectional Range, is considered the primary navigation aid for the National Airspace System (NAS) due to its widespread use and reliability in providing aircraft with precise navigation information. VOR stations transmit signals that allow pilots to determine their bearing relative to the VOR station, facilitating en-route navigation as well as approaches and departures at airports.

VOR systems are well-established within the NAS, have a high level of accuracy, and are supported by a robust infrastructure. Pilots are trained extensively on VOR navigation, and it forms a critical part of IFR (Instrument Flight Rules) operations. The use of VOR allows for effective air traffic management and enhances safety by providing clear and consistent navigational references for aircraft.

While other navigation aids like NDB (Non-Directional Beacon), GPS (Global Positioning System), and ADF (Automatic Direction Finder) play important roles in navigation as well, VOR remains the mainstay for traditional navigation within controlled airspace, due in part to its compatibility with existing air traffic control procedures and its operational reliability.