Nowadays, robots are getting popular; they are being deployed everywhere, ranging from farms, homes, hospitals to industries, warehouses, and military operations. The field of autonomous robotics is becoming popular day by day. Advancement in electronics and mechanical designs can be considered the driving force for the advancement of autonomous robots. To develop an autonomous robot that can work with humans, the robot must perceive the surrounding and decide by itself the next action it should perform at each instant of time. In this paper, we present a mathematical model based autonomous quadcopter which can reach any given desired location from its initial position in an outdoor environment. Taking the desired position and orientation of the quadcopter in 3D space from the user, the system generates an optimal trajectory for the quadcopter to follow from initial position and orientation to final position and orientation. The entire pipeline with different methods of trajectory generations, the non-linear and coupled dynamic model of the quadcopter, linear and nonlinear controller development for autonomous flight is explained in this paper. Quadcopter encounters unknown air resistance and drag forces in the outdoor environment; we have discussed the problem of unknown disturbances occurring during the flight.