These machines are mainly used by military and police officers to carry out an operation where a manned aircraft seems impractical or too risky. Unmanned aircraft are not new; they have been in use since the World War I. However, at that time the control was mechanical and the aircraft could only go as far as the fuel would allow.
Later on, devices that could be controlled with the help of radio or infra-red technology were developed. These devices became the predecessors of the modern quadcopter that employs integrated circuit or computer chips and can be programmed to fly for a definite time period in a definite direction fulfilling a definite purpose.