“…Considering that training costs are affected by annual price fluctuations and standardized training programs of airlines, it is more practical to classify training costs. Based on the recommendations of relevant professionals, this study grades training costs in 2020 according to the following intervals: [0, 5), [5,15), [15,25), [25,35), and [35, ∞), which correspond to the five grades A, B, C, D, and E, respectively. The cost grades for the six tranche types of training are shown in Table 9.…”