# Safety Evaluation Method and Management Strategy for Aviation Flight Plans
## 2 Literature Review
(2016) proposed an integrated robust optimization model based on aircraft scheduling by quantifying the robustness of the overall flight plan and the operating costs to achieve flight optimization, effectively reducing the cost of the aircraft delays. All five of these studies took system robustness as their research object to achieve flight plan optimization from an economic perspective. However, the reduction in the flight plan delays and aircraft conflicts was not fully considered. Using the above research as a basis, [PERSON] et al. (2016) established a flight planning optimization model based on the improvement of the robustness to reduce the costs of the delays, but they did not consider the costs of aircraft scheduling and exchange. [PERSON] et al. (2016) solved the problem of aircraft sequencing by minimizing the total weighted delay of the aircraft landings and takeoffs to reduce the flight delays. [PERSON] et al. (2016) used AnyLogic to establish an airport scene operation simulation model in order to identify the bottleneck link in the flight delays,and then, they optimized the flight times according to the bottleneck link to reduce the delays to the flight plans. [PERSON] et al. [20] established a flight schedule optimization model for a group of airports to determine the highest flight punctuality rate. [PERSON] et al. [21] established an optimization model for takeoff flight slots that considered the actual release capacity and control interval of the airports to reduce the flight delay losses. In general, most of the current approaches to the management of flight plans focus on the economic benefits, considering only the problem of aircraft sequencing and the optimization of the takeoff and landing times. This has led to flight delays becoming a recurring problem, especially in high-volume, high-density, and complex airspace. This extensive flight management and adjustment framework can neither avoid the shortcomings--such as low operational efficiency and the high risk of aircraft conflict--nor sufficiently guarantee the safety of the aviation operations. Under the framework of the four-dimensional tracking operation which is proposed for next-generation air traffic systems, air traffic safety assurance can be advanced to the strategic phase of flight plan formulation and adjustment, and the operational safety of air traffic can be ensured from a strategic point of view using a reasonable flight plan that considers safety. Most studies and our previous research have devoted great attention to tactical aircraft conflict detection and resolution, addressing how to improve the prediction accuracy of flight trajectories and how to generate conflict-free trajectories while flights are in progress. This study primarily focuses on conflict avoidance in the strategic phase by evaluating the safety levels of the flight plans and adjusting those plans with a low safety index. In this way, potential conflicts are expected to be avoided by adjusting the flight plans to the maximum extent, and the task of safety assurance is advanced before the aircraft takes off. This method provides a new framework to evaluate the safety of the flight plans, while also improving the management strategy of the flight plans so that they pay attention not only to economic benefits, but also to safety. Improving the flight plan management strategy from the perspective of conflict prevention is expected to fundamentally reduce the probability of conflict and the workload of the controllers and pilots during the flights, while also improving the safety of the whole air transport system. The remainder of this paper is structured as follows: After the overview of the previous studies on flight plan management in Section 2, the evaluation of flight plan safety is elaborately illustrated in Section 3. Section 3.1 classifies the aircraft conflict into three different types. Section 3.2.1 introduces the concept of aircraft-accessible areas, which is the fundamental basis of the conflict probability quantification and safety index evaluation.