In this paper, an offline flight planner that computes an efficient coverage trajectory for a quad-rotors UAV is presented. The planner consists of three steps: mission definition, automatic path planning and trajectory generation. The proposed planner, as a useful tool, allows an UAV operator to easily define and generate a coverage trajectory for any specific task. The resultant trajectory can be dispatched to a quad-rotors with trajectory tracking controller for the missions that require a complete area coverage.