# Safety Evaluation Method and Management Strategy for Aviation Flight Plans
## 4 Flight Plan Management Strategies Based on the Safety Index  
The safety index can be used to evaluate the safety of the flight plan. After the future safety index of each aircraft is determined, the safety index can be classified into grades.  
1. High safety index: The safety index is greater than the specified threshold is.
2. No guarantee of safety: The safety index is greater than 0, but it is less than the specified threshold.
3. Low safety index: The safety index is highly approaching 0.  
The safety assessment module displays the conflict time of the low-safety aircraft and the location range that is involved in the conflict in the form of a list; it also displays the specific location of the potential conflict in the form of image information. Different colors are used to differentiate between the high and low levels of the safety index and to prioritize conflicts. The warning index displays security notifications for flight plan according to the following conditions:  
1. Case 1: If no conflict risk is detected in the flight plan, then no alarm will be issued;
2. Case 2: If a conflict risk is detected in the flight plan, then an alarm will be issued. The alarms can be classified into the following types: 1. Red warning: For an aircraft with a low safety index in the flight plan, if the safety index is less than the specified threshold, then the air traffic control must negotiate with the airlines to adjust the flight plan as the first priority.
2. Yellow warning: An unsafe aircraft can be found in the flight plan, and a certain risk of potential conflict exists. The controller must inform the aircraft that is involved of the conflict risk situation and pay close attention to the status of the aircraft.
3. Green warning: If an aircraft enters a special airspace or flight restriction area, the air traffic control must negotiate with the airlines to appropriately adjust the flight path.  
The responses of the air transport systems to the safety indices include the following three conditions:  
1. High safety index--there is no need to consider flight plan optimization.  
The airline can follow the predetermined plans to complete the flight tasks without the fear of conflict with other aircrafts. The controllers can reduce the level of surveillance of the aircraft during the flight.
2. Safety is not guaranteed--the conflict avoidance task is negotiated by the aircraft pilot and the controller.  
The pilot of the aircraft can autonomously determine the trajectory, but they require feedback from the controller. The controller will judge whether the flight path that has been submitted by the pilot is feasible on the basis of the feedback information from other aircraft and the surrounding environmental information. The flight trajectory can be followed with the permission of the controller, who must also share the trajectory information of the aircraft with the surrounding aircraft and improve the monitoring level of the aircraft.
3. Low safety index--the system must be warned, and the flight plan should be adjusted.  
The air traffic control and the airlines must negotiate to adjust and optimize the flight plans. Moreover, a secondary safety assessment of the optimized flight plan should be carried out until all of the part of the flight plan achieve a safe level.