In this paper, a gradient decent based methodology is employed to tune the Proportional-Integral-Derivative (PID) controller parameters for AR Drone quadrotor. The three PID controller parameters, proportional gain (Kp), integral gain (Ki) and derivative gain (Kd) are tuned online while flying. The proposed technique has been demonstrated through two test cases. One is the way-point navigation and other is the leader-follower formation control. The experimental result as well as simulations result have shown for both the cases.