Formation flight can effectively reduce aircraft operating costs and increase airspace capacity. Taking the three-aircraft formation as the research object, the dangerous area and the optimal position of the No. 3 aircraft in the formation were determined first. Then, based on the aircraft performance and particle swarm optimization algorithm, the formation scheme of No. 3 aircraft without changing the path of No. 1 and No. 2 aircraft was proposed, and the influence law of the airport location of No. 3 aircraft on the formation assembly point and separation point was revealed. Finally, Hough transform and DBSCAN clustering algorithm were used to process the great circle route, and the air corridor was obtained as the initial solution, and then the whale optimization algorithm was used to optimize it, and the auxiliary corridor was established, which provided a feasible solution for the path planning problem of large-scale formation. The results show that when the longitudinal distance between No. 3 aircraft and No. 1 aircraft is 6000m, the optimal position of the formation of No. 3 is -57m or 114m, and the optimal position of No. 3 is affected by the weight of No. 1 and No. 2. When the distance between the takeoff or landing airport of No. 3 aircraft and the great circle of the formation route is constant, the optimal assembly Angle or the optimal separation Angle is basically unchanged. Taking 827 trans-Pacific flights as an example, five air corridors were obtained through Hough transform and DBSCAN clustering. When the threshold of distance between the take-off and landing airport and the air corridor is 300km, the percentage of flights that can use the corridor reaches 54.17%. After the optimization of the whale optimization algorithm, the percentage increased to 64.33%.