In recent years, Unmanned Air Vehicles (UAV) are gaining popularity among hobbyist, university-level researchers and military agencies. This paper presents the enhancement of a commercial-off-the-shelf (COTS) product that is capable of achieving semi-autonomous flight. The details of the selection of various components and software design are discussed. Take-off, hovering and landing controls for indoor flying capabilities are achieved by deriving the mathematical model of the quadcopter dynamics. Altitude control algorithm is implemented to ease the burden of the pilots. The final design of the quadcopter fulfils the flight capability and the required stability.