noun
Refers to any aircraft that operates without a human pilot on board, including military drones and civilian UAVs.
無人飛行機が荷物を配達する実験が行われた。
An experiment was conducted in which an unmanned aircraft delivered packages.
ドローン is the common loanword for multi-rotor consumer/commercial drones, while 無人飛行機 is a broader technical term covering all unmanned aircraft including fixed-wing military UAVs.
Compound of 無人 (mujin, 'unmanned') + 飛行機 (hikōki, 'airplane').