Economic and Environmental Impacts of Green Investments in Airports: Input–Output and Differences Analysis in Türkiye

This study analyzes the economic and environmental impacts of green investment practices implemented at four major airports in Türkiye---İstanbul, Sabiha Gökçen, Esenboğa, and Adnan Menderes---over the period 2015--2024. The analysis combines input--output and difference-in-differences methods to assess the effects of green energy transformation and sustainable aviation policies on regional economic growth, employment effects, competitiveness, and carbon reduction. Input-Output results indicate that green investments generate strong regional multiplier effects, with gross domestic product contributions ranging between 1.45 and 1.60 units per unit of investment, and positive employment impacts measured in job years. Environmental performance is also significant: carbon efficiency ranges between 214 and 233 tons of CO2 reduced per million USD invested, with Istanbul Airport exhibiting the highest performance. DID estimates show that airports adopting sustainable aviation fuel experience statistically significant improvements in competitiveness despite higher short-term costs. Policy scenario comparisons further suggest that a 20% fossil fuel tax is more effective than a 17% fuel subsidy in stimulating green investment. Overall, the findings demonstrate that airport-level green transformation delivers dual environmental and economic benefits. These results provide strong empirical evidence that accelerating green investments to support a sustainable aviation transition in Türkiye can play a critical role in ensuring long-term resilience in the sector by enhancing international competitiveness.