Which government agency regulates unmanned aircraft systems?

The Federal Aviation Administration (FAA) is the government agency responsible for regulating unmanned aircraft systems (UAS). This includes establishing rules for the operation, certification, and airworthiness of these aircraft, ensuring safety in national airspace. The FAA's role encompasses the oversight of all civil aviation, which extends to commercial and recreational use of drones, training requirements for pilots, and issuing regulations that govern the use of UAS in various environments.

Other agencies have roles in related areas—such as the National Aeronautics and Space Administration (NASA), which focuses on aerospace research; the Department of Transportation (DOT), which oversees national transportation policy but does not specifically regulate aviation; and the Federal Communications Commission (FCC), which manages communication licenses and spectrum but not the aircraft themselves. Hence, the FAA's specific mandate towards the regulation of unmanned aircraft systems distinguishes it as the correct answer.