Tripartite evolutionary game of route subsidies for small and medium-sized airport groups based on composite system synergy model

With the development of the air transport industry, the role of small and medium-sized airport groups (SMSAGs) in expanding air coverage and promoting balanced regional development has become increasingly prominent. However, their integrated operation faces challenges such as interest coordination among multiple subjects, and the route subsidy policy is a key instrument to address this issue. This paper focuses on SMSAGs as the research object, combines the Composite System Synergy (CSS) model, and explores the tripartite game among airports, airlines, and passengers in the context of route subsidies. Firstly, an evaluation index system for the synergy degree of SMSAGs is constructed from three subsystems: civil aviation transportation, urban development, and ground transportation. The coordinated development level is quantified through the order degree of subsystems and the synergy degree of composite system. Secondly, a tripartite evolutionary game model is established under the scenario where SMSAGs initiate an integrated operation mode due to weather conditions. The dynamic evolution process of strategy selection by airports, airlines, and passengers, as well as the stability of system equilibrium points, are analyzed. Finally, an empirical analysis and numerical simulation are performed using the Baoshan-Tengchong-Mangshi (BTM) airport group in Western Yunnan Province as a case study. Findings indicate that the synergy degree of SMSAGs exerts a phased impact on route subsidy strategy selection: when the synergy degree is low, airports tend to adopt a “variable subsidy” strategy, whereas they tend to shift toward a “fixed subsidy” strategy when the synergy degree is high. Factors such as passenger transfer probability, airline service level, incremental passengers, and ticket prices significantly influence the direction of system equilibrium. The research results can provide a theoretical basis and practical reference for the coordinated development of SMSAGs and the optimization of route subsidy policies.