Definition
Aeronautical charts published by the FAA for instrument flight rules (IFR) navigation at altitudes below 18,000 feet MSL. They depict Victor airways, navigation aids (VORs, NDBs), intersections, minimum en route altitudes, controlled airspace, and reporting points used during the en route phase of an IFR flight.
Plain English
A map pilots use when flying on instruments below 18,000 feet. It shows the routes, radio navigation aids, altitudes, and airspace they need to follow.
Context Anchor
You will see these charts during instrument flight planning, while choosing a route, and during the en route portion of a flight below the high-altitude structure.
Derivation
En route' comes from French, meaning 'on the way.' These charts cover the on-the-way portion of a flight — the cruise segment between departure and arrival — at lower altitudes, distinguishing them from the High Altitude Charts used at and above 18,000 feet.
Why Pilots Care
They provide the essential route and navigation information required for safe IFR operations in the low-altitude structure.
Intuition Check
“Low altitude” does not mean close to the ground here. In this chart name, it means the lower instrument en route chart system, generally used below 18,000 feet above mean sea level.
Example Sentence 1
Before departing, she pulled up the current En Route Low Altitude Chart to confirm the minimum en route altitude for V25.
Example Sentence 2
Before filing the IFR flight plan, she checked the En Route Low Altitude Charts for any temporary flight restrictions along the route.