Plain English Meaning

How well the aircraft can know where it is and stay on the path it's supposed to fly. It's a stated standard the airplane and its equipment must meet — not just a vague idea of being on course.

Full Definition

A measurable standard of how accurately, reliably, and consistently an aircraft's navigation system can determine and maintain its position along an intended flight path. In modern airspace, navigational performance is expressed as a required level of accuracy (for example, RNP 1 means the aircraft must stay within 1 nautical mile of the intended track 95% of the time) along with associated requirements for integrity, , and onboard .