The issue of formation rearrangement for a troop of cooperative unmanned vertical takeoff and landing (VTOL) aircrafts in an obstacle-loaded atmosphere is figured out using a purposed backstepping based proportional-integral-derivative controller (PID). The designed controller is developed to regulate every unmanned quadrotor within the troop in an exceedingly localized manner guaranteeing the reserving of the required geometric formation. The backstepping technique could be a promising control technique for nonlinear and coupled multivariable systems. The essential contribution in this paper concentrates on resolving the formation issue for a troop of cooperative pilotless VTOL airplanes in a decentralized manner via backstepping PID regulator. The designed decentralized controller guarantees the success of the required mission of the swarming troop. The simulation results declare the successes of the proposed controller in guaranteeing the stability of the system and reserving of the desired geometric formation either within the existence or absence of obstacles. I. Introduction In recent decenniums, unmanned aerial vehicles (UAVs) have charged a mature concern with their success among achieving heaps of progress in several applications in each military and civilian scopes [1-3]. The UAV is characterized by its capacity to accomplish its assignments in alleged "D-cube" operations (Dull-Dangerous-Dirty) atmosphere with no risk for manned pilots resources [4, 5], easy to preserve and low worth. Therefore, UAV has attained growing concern from scientists, researchers, and engineers. UAVs may be thought about as a hopeful alternative for numerous pilotless military and civilian exercises [6-8]. The auspicious results of a single UAV in executing varied applications persuade the utilization of multiple UAVs cooperating collectively to meet the required tasks [9-11]. Cooperative UAVs guarantees the success of the desired missions with better performance compared with single UAV [12-15]. Certain strategies are needed for multiple cooperative UAVs to cooperate collectively to fulfill the required goals. These strategies which defined by the cooperative UAVs attributes are known as UAVs tactics. These tactics can be classified into the swarming, mission duty, structure rearrangement, and active blockade [16, 17]. Formation rearrangement is outlined by the power of the multiple cooperative UAVs to preserve a desired geometric structure [12], and reconfigure to a different formation per the surrounding circumstances guaranteeing the success of the required application [16, 18]. Each member in the cooperative UAV troop must respect Reynold's rules of flocking during its formation [19-21]. Each UAV member has to match its velocity and separating distance from its neighbors and avoid colliding with its neighbors or obstacles [22]. There are several varieties of controls in the formation rearrangement of multiple cooperative UAVs domain. The scope of these control techniques steadily growing fast last decade including hybrid ...