Definition
An IFR aeronautical chart that depicts the airway structure, navigation aids, intersections, and other information used for instrument flight at and above 18,000 feet MSL within the conterminous United States. It shows jet routes, high-altitude reporting points, and the navigation facilities and frequencies needed to fly them.
Plain English
A chart designed for instrument flying high up — at or above 18,000 feet. It shows the high-altitude routes pilots follow, the radio navigation stations they use, and the reporting points along the way.
Context Anchor
Seen during IFR flight planning and en route flying when the planned route uses the upper-altitude instrument route system, especially at or above 18,000 feet.
Derivation
En route comes from French and means “on the way.” In aviation, it means the part of a flight after departure and before arrival; high-altitude narrows the chart to the upper-altitude route system.
Why Pilots Care
These charts ensure pilots follow the correct high-altitude route structure, maintain safe separation from terrain and traffic, and comply with ATC clearances.
Intuition Check
High-altitude does not just mean any chart used when flying over mountains or at a personally “high” altitude. Here it means the specific IFR en route chart for the upper-altitude route structure, generally beginning at 18,000 feet above mean sea level.
Example Sentence 1
Before her cross-country flight at FL350, she pulled out the high-altitude en route chart to review the jet routes.
Example Sentence 2
Before filing the flight plan, the crew checked the high-altitude en route chart for any restricted airspace along the route.