Definition
Preferred IFR routes — typically jet routes — that are published for use in one direction only. They are established to streamline traffic flow at high altitudes and reduce conflicts between opposing streams of aircraft.
Plain English
Certain high-altitude routes are one-way streets. You can only fly them in the published direction.
Context Anchor
Seen when planning or reviewing instrument routes, especially in preferred route listings and air traffic control clearances.
Why Pilots Care
These routes reduce the chance of head-on conflicts and let controllers handle more traffic smoothly without constant rerouting.
Analogy
It is like a one-way street in the sky: the route exists to move traffic safely and predictably in one direction.
Intuition Check
Do not read this as any route that happens to be flown in one direction on a particular day. In this context, it means a published route designed for one-way use.
Example Sentence 1
When planning the eastbound leg, the dispatcher selected a single direction route published for eastbound traffic only.
Example Sentence 2
We filed single direction routes across the North Atlantic to comply with the published one-way flow.