Definition
Any ground-based or space-based facility, transmitter, or visual device used by aircraft in flight to determine position, follow a course, or conduct an instrument approach. Common examples include VOR, DME, TACAN, NDB, ILS components, and GPS satellite systems.
Plain English
A piece of equipment, on the ground or in space, that helps a pilot figure out where they are or where they need to go.
Context Anchor
Pilots see this term in charts, flight planning, instrument procedures, air traffic control instructions, and discussions of navigation equipment.
Derivation
A blend of 'navigation' (from Latin navigare, 'to sail or steer a ship') and 'aid' (a help or assistance). The aviation use carried the maritime idea of fixed signaling stations into the air — beacons and transmitters that help a pilot stay on course the way buoys and lighthouses helped ships.
Why Pilots Care
NAVAIDs supply the position and course data needed for safe flight when visual references are unavailable.
Intuition Check
Do not assume a NAVAID is only one kind of radio beacon. In aviation, the term can cover several kinds of approved navigation help, including visual references and electronic or space-based systems.
Example Sentence 1
The pilot checked NOTAMs and saw that the VOR NAVAID at the destination was out of service for maintenance.
Example Sentence 2
GPS has replaced many older ground-based NAVAIDs for most cross-country flights.