Definition
A Required Navigation Performance (RNP) route on which the aircraft must keep its position within 1 nautical mile of the centerline for at least 95 percent of the total flight time, and must have onboard performance monitoring and alerting that warns the pilot if this accuracy cannot be met. RNP 1 routes are typically used in the terminal environment, including departures, arrivals, and transitions between en route and terminal phases.
Plain English
A flight path where the airplane's navigation system has to stay within 1 mile of the line on the chart almost all the time, and it has to tell the pilot if it can't.
Context Anchor
Seen on instrument charts, route descriptions, clearances, and flight planning material where a route has an RNP 1 requirement.
Derivation
The '1' refers to the lateral accuracy in nautical miles. RNP comes from 'Required Navigation Performance' — the word 'required' is key: it's not just what the aircraft can do, it's what the route demands and what the system must confirm it can deliver.
Why Pilots Care
Determines whether an aircraft is approved to use more direct, fuel-efficient routes that are not available to less capable navigation systems.
Grounding Statement
Think of the route as having a centerline, and the aircraft must be able to stay close enough to that centerline while also warning the pilot if it cannot.
Intuition Check
Do not read the 1 as a route number or difficulty level. In RNP 1, the 1 means 1 nautical mile of required navigation accuracy.
Example Sentence 1
The arrival into the terminal area was published as an RNP 1 route, so the crew confirmed the FMS was operating within tolerance before commencing the descent.
Example Sentence 2
Before accepting the RNP 1 route clearance, the crew confirmed the aircraft's navigation certification.