Plain English Meaning

It is a code letter you put on the flight plan to tell controllers what your aircraft's navigation gear can do. The letter tells them whether you can fly direct routes using onboard navigation, and what kind of approaches and procedures you are allowed to fly.

Full Definition

A single letter placed after the aircraft type designator in Item 10 of the ICAO flight plan (or the equivalent field in a domestic FAA flight plan) that tells ATC what navigation, communication, and surveillance equipment the aircraft has on board and is approved to use. The suffix identifies whether the aircraft is RNAV-capable, what level of RNAV or RNP it supports, and whether it has transponder, DME, GNSS, and other equipment relevant to routing and .