A UAV is an aircraft (such as a drone) with no pilot on board. UAVs come in two varieties: (1) controlled from a remote location and (2) flying autonomously. Autonomous flight continues to develop from pre-programmed flight plans towards flight and decisions derived automatically from specification of a task or objective. Military UAVs perform reconnaissance as well as attack missions. UAVs are also used in a small but growing number of civil applications, such as firefighting and crop spraying.