Definition
An aeronautical chart published by the FAA for instrument flight rules (IFR) navigation below 18,000 feet mean sea level. It depicts the low-altitude airway structure, including Victor airways, navigation aids, intersections, minimum en route altitudes, controlled airspace boundaries, communication frequencies, and airports with instrument approaches.
Plain English
A flight map used by pilots flying on instruments at lower altitudes. It shows the routes, radio aids, altitudes, and airspace they need to fly safely from one airport to another.
Context Anchor
Seen during IFR flight planning and in the cockpit while flying the en route portion of an instrument flight.
Derivation
"En route" comes from French, meaning "on the way." The name describes exactly what the chart is for: navigating while on the way between airports, under instrument flight rules, at lower altitudes.
Why Pilots Care
It provides the airway structure, minimum altitudes, and navigation references needed to maintain safe obstacle clearance and comply with IFR routing.
Analogy
It is like a road map for IFR flying, but instead of highways and exits it shows published air routes, navigation points, safe minimum altitudes, and radio information.
Intuition Check
“Low altitude” does not mean flying close to the ground. Here it means the FAA’s lower IFR en route chart structure, generally used below 18,000 feet MSL.
Example Sentence 1
Before departure, she pulled up the IFR En Route Low Altitude Chart to check the minimum en route altitude along the airway.
Example Sentence 2
Before departure the instructor and student reviewed the IFR En Route Low Altitude Chart to select an alternate route with adequate navigation coverage.