Definition
An aeronautical chart used for instrument flight navigation below 18,000 feet MSL, depicting Victor airways, navigation aids, intersections, minimum altitudes, controlled airspace, and other information required to fly IFR in the low-altitude structure.
Plain English
A flight map for instrument pilots flying below 18,000 feet. It shows the airways, navigation stations, and altitudes needed to fly safely on instruments at lower levels.
Context Anchor
Seen during IFR route planning and in flight when a pilot is navigating between airports using published instrument routes.
Derivation
"En route" comes from French, meaning "on the way." The name simply describes the chart's role: a chart for the low-altitude portion of the route between departure and destination.
Why Pilots Care
Provides the precise route and altitude information needed to conduct safe IFR flight in the altitude band used by most piston and light turbine aircraft.
Intuition Check
Low-altitude does not mean the chart is for flying close to the ground. Here it means the chart covers the lower instrument route system, as opposed to the high-altitude chart system.
Example Sentence 1
Before departure, she pulled up the low-altitude en route chart to review the Victor airways and minimum en route altitudes for her IFR flight.
Example Sentence 2
Before filing the IFR flight plan, she reviewed the low-altitude en route chart to select a route with suitable navigation aids.