Airline environmental efficiency measures through a non-convex meta-frontier DEA model

To mitigate the impact of aviation on climate change, the International Civil Aviation Organization (ICAO) has committed to reducing carbon dioxide (CO₂) emissions from international aviation by 5% by 2030 and to achieving net-zero carbon emissions by 2050. It is therefore essential to assess the environmental efficiency of airlines to urge them to adjust their actions promptly to meet the desired strategic objectives. This paper focuses on assessing the environmental efficiency of airlines using a network structure and constructs a three-stage airline network structure. Then, a non-convex meta-frontier DEA model with unified natural disposability and managerial disposability is proposed to assess the overall efficiency of 85 airlines for 2018–2019, based on data from 85 airlines worldwide for 2018–2019. The new model not only automatically determines whether an airline's inputs are natural or managerial disposable, but also measures the environmental efficiency of each region, while optimizing overall efficiency. Firstly, Ryanair has the highest overall efficiency among the 85 airlines in 2018–2019, and this increased efficiency is closely related to its excellent performance in handling carbon dioxide emissions. Secondly, the airline efficiency rankings obtained from the non-convex meta-frontier model and the convex meta-frontier model proposed in this paper are largely in line with each other.