An aircraft is a fixed-wing aircraft that is propelled forward by thrust from a jet engine, propeller, or rocket engine. Airplanes come in a variety of sizes, shapes, and wing configurations. The broad scope of aircraft uses includes entertainment, transport of goods and people, the military, and research. Worldwide, commercial aviation transports more than four billion passengers annually on aircraft and transports more than 200 billion tons km of cargo annually, which represents less than 1% of the world's freight traffic. Most aircraft are operated by an onboard pilot, but some are designed to be remote-controlled or computer-controlled like drones.