Plain English Meaning

A set of official flight routes that aircraft follow using onboard navigation equipment instead of flying from one ground station to the next. Because the routes don't depend on ground transmitters, they can be drawn as straight lines between useful points, making flights more direct.

Full Definition

A network of published air routes that uses area navigation (RNAV) rather than ground-based navigation aids. RNAV allows aircraft to fly directly between any two defined points in space, so these routes are not tied to the location of VORs, NDBs, or other physical navaids. The system includes high-altitude Q-routes (used in the jet route structure above 18,000 feet MSL) and -altitude (used below 18,000 feet MSL).