Definition
A heading used in the Aeronautical Information Manual glossary to introduce the standard categories of established air routes used in the National Airspace System, such as airways, jet routes, RNAV routes, and military training routes. It is not itself the name of a route — it is a section label under which each defined route type is listed and described.
Plain English
This is the title of a glossary section that lists the official kinds of air routes pilots use. It groups the names and meanings of those route types together in one place.
Context Anchor
Seen in FAA glossary material and procedure discussions for published instrument departures and arrivals.
Derivation
Route comes from an old French word for a road or way. Defined comes from Latin roots meaning to set limits or boundaries. Together, the phrase points to a path whose limits and use have been clearly set, not left open to guesswork.
Why Pilots Care
Using defined routes maintains traffic separation and ensures regulatory compliance during IFR operations.
Intuition Check
Do not read Routes Defined as a casual heading meaning “some routes are listed here.” In FAA use, it means the route parts are being specifically identified so pilots and controllers share the same understanding of the path.
Example Sentence 1
Under the AIM glossary heading Routes Defined, the student found entries for airways, jet routes, and RNAV routes.
Example Sentence 2
Pilots prefer defined routes in busy terminal areas because they simplify navigation and separation.