The situation under lowaltitude airspace is much more complex and dangerous, and especially it is difficult to keep safety of aircraft when many aircraft are in a limited airspace. Therefore, it is necessary and important to develop path planning methods under low-altitude airspace which is the key technology to keep aircraft safety. Path planning for aircraft under the low-altitude airspace is to optimize the paths for aircraft with consideration of avoiding the obstacles and satisfying the physical constraints of aircraft. However, it is difficult to solve the characteristics such as multiobjective, many constraints and tightly coupled. Path planning for multiaircraft under the lowaltitude airspace is researched. An adaptive multi-objective evolutionary algorithm with heuristics operator and adaptive differential evolution multi-objective algorithm is propsed. The model of collision avoidance for aircraft is established firstly. Then, the cooperative coevolution is introduced to the proposed method. Each aircraft optimizes its path by using the multiobjective optimization algorithm, and avoids collision through cooperation among different aircraft. The experimental results show the proposed method is effective and can obtain optimal paths for aircraft in real time.