Unmanned aerial vehicle ( UAV ) Also known as a Unmanned aircraft System (UAS) or a remotely piloted aircraft (RPA) or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot (called a Combat Systems Officer on UCAVs) or autonomously, that is, as a self-directing entity. Their largest use is within military applications. To distinguish UAVs from missiles, a UAV is defined as a "powered, aerial vehicle that does not carry a human operator, uses aerodynamic forces to provide vehicle lift, can fly autonomously or be piloted remotely, can be expendable or recoverable, and can carry a lethal or nonlethal payload". Therefore, cruise missiles are not considered UAVs, because, like many other guided missiles, the vehicle itself is a weapon that is not reused, even though it is also unmanned and in some cases remotely guided.
There are a wide variety of UAV shapes, sizes, configurations, and characteristics. Historically, UAVs were simple drones (remotely piloted aircraft), but autonomous control is increasingly being employed in UAVs. UAVs come in two varieties: some are controlled from a remote location (which may even be many thousands of kilometers away, on another continent), and others fly autonomously based on pre-programmed flight plans using more complex dynamic automation systems.
Currently, military UAVs perform reconnaissance as well as attack missions. While many successful drone attacks on militants have been reported, they have a reputation of being prone to collateral damage and/or erroneous targeting, as with many other weapon types. UAVs are also used in a small but growing number of civil applications, such as firefighting or nonmilitary security work, such as surveillance of pipelines. UAVs are often preferred for missions that are too "dull, dirty, or dangerous" for manned aircraft.
