This document contains the Minimum Aviation System Performance Standards (MASPS) for a C21 Link System connecting a Control Station (CS) and an Unmanned Aircraft (UA).2 It covers UA operations requiring a C2 Link System3 that allows the UA to operate within visual line of sight (VLOS) and beyond visual line-of-sight (BVLOS) of a CS. The types of information that are exchanged over the C2 Link System include both:

1. The commands from the remote pilot,4 i.e., the telecommands sent over a forward link from the CS to the UA, and

2. The status and annunciations from a UA, i.e., the telemetry data sent over a return link from the UA to the CS, that are associated with all of the activities the remote pilot is required to perform to safely execute the flight plan. These safety-of-flight5 related information exchanges do not include normal payload information, i.e., the information associated with the UA mission payloads.

A more complete description of those information exchanges and the associated requirements on the C2 Link System are given within this MASPS.