As the demand for air traffic increases, new air traffic management systems are needed. In the system, it is expressly necessary to avoid conflict between aircraft. Efficient methods to prevent conflict are currently based on the expertise of air traffic controllers. Hence, a two-step analysis method is described in this study. First, it is shown using a proposed method with en route radar track data that no conflicts occurred in the airspace over Japan during the period in question. Second, instructions provided to pilots by the air traffic controllers to solve conflicts are estimated from the same radar data, and the results allow some groups to be rearranged in terms of avoidance procedures. These results will be useful references when developing an automated system of conflict detection and resolution in the future.