In this paper, we deal with an obstacle avoidance control for a PVTOL (Planar Vertical Takeoff and Landing) aircraft. One of the effective approaches is to formulate such a problem in the framework of optimal control with penalties in the cost functions, and thus any existing optimal control design method is applicable. Based on the 'virtual space' approach, we formulate the obstacle avoidance problem as an unconstrained optimal control problem. We design a transform function for making an unconstrained virtual space. The model of the PVTOL aircraft is represented as a descriptor form. Then, we propose a solution to the descriptor form. The effectiveness of our approach is confirmed by numerical experiments.