Definition
Aeronautical charts produced by the FAA for instrument flight rules (IFR) navigation at or above 18,000 feet MSL. They depict the jet route system, very high frequency omnidirectional range (VOR) navigation aids used in that airspace, controlled airspace boundaries, reporting points, and other data needed for high-altitude IFR operations.
Plain English
These are the maps pilots use when flying high — at or above 18,000 feet — under instrument rules. They show the high-altitude routes, navigation stations, and the information needed to fly safely in that airspace.
Context Anchor
Seen during instrument flight planning and in the cockpit when a pilot is choosing or following a higher-altitude route between airport areas.
Derivation
En route comes from French and means “on the way.” In aviation, it means the middle part of a flight between the departure area and the arrival area. High altitude tells you these charts are for the upper route system, not the lower-level route charts.
Why Pilots Care
They supply the route, fix, and airway data required for ATC compliance, terrain clearance, and traffic separation at high altitudes.
Intuition Check
“High altitude” does not mean any flight that seems high. Here it refers to the FAA chart series for the upper instrument route system, generally starting at 18,000 feet mean sea level.
Example Sentence 1
Before the flight to FL350, the captain pulled up the current En Route High Altitude Charts to review the jet routes along their planned course.
Example Sentence 2
Before departure the crew reviewed the En Route High Altitude Charts to choose the most direct airway at their planned flight level.