An Airthorn is an enemy from Metroid Prime 2: Echoes. It is only found in one room, and cannot be scanned in normal gameplay. The Airthorn can only be seen and scanned from within a Secret World in the Dark Transit Station.
These mechanisms were created by the Luminoth during the war against the Ing. They would patrol the skies to inform their creators of any possible danger, much like the Sentreyes, though the latter were designed to watch over ground terrain.