Definition
A published network of fixed routes used by aircraft operating in the high altitude airspace structure, typically at or above FL180 in the United States. These routes provide defined paths between navigation fixes for en route operations above the low altitude airway system.
Plain English
A set of established sky-roads used by aircraft flying at high altitudes, giving pilots and controllers agreed paths to follow between points on the map.
Context Anchor
Seen in FAA acronym lists, high-altitude flight planning, high-altitude charts, and air traffic control route clearances.
Why Pilots Care
Using a published high altitude route keeps the aircraft on a known, charted path that controllers expect, which simplifies clearances, separation, and navigation at cruise altitudes.
Intuition Check
Do not read “route system” as one single route. Here it means a published network of high-altitude routes used by pilots and controllers.
Example Sentence 1
The flight plan filed the aircraft along the high altitude route system from the departure area to the arrival fix at FL350.
Example Sentence 2
Before departure the pilot reviewed the current HARS segments available for the planned altitude.