What is a companion computer?

A drone has two brains. The flight controller is a real-time board that stabilizes and steers the aircraft, running firmware such as ArduPilot, PX4, Betaflight, or iNav. The companion computer is a general-purpose Linux computer that sits next to it and does everything the flight controller was never meant to: encode and stream HD video, carry a long-range radio link, connect to the cloud over 4G or 5G, run computer-vision models, and execute higher-level autonomy.

The two connect over MAVLink, the open drone messaging protocol. The flight controller flies the aircraft; the companion computer makes it smart. Because the companion computer is a normal Linux machine, its capabilities are software, so they can be updated and extended long after the airframe is built.