6. Conclusions
This study explores strategic airline operations in response to a carbon-constrained air transport market. Moreover, the study aims to confirm the effects of carbon-constrainterelated regulations such as those of the EU-ETS for a theoretical airline based outside the EU. We develop a nonlinear mathematical model formulation and propose an efficient genetic algorithm to consider countermeasures involving aircraft reassignment and flight route adjustment. With this numerical example, we verify our model and our solution method using hypothetical system parameters as applied to the EU-ETS situation. According to the resulting comparison between the cases before and after the EU-ETS, we find that an airline tends to decrease the long-haul flight routes assigned to inefficient aircraft and increase the short-haul flight routes. The more efficient aircraft tend to be concentrated on several longer flight routes rather than serving a greater diversity of routes. Through these changes to operations, the quantity of carbon emission from inefficient aircraft is reduced and that from efficient aircraft is increased. As a result, under the EU-ETS restrictions, the overall quantity of carbon emissions for the hypothetical airline decreases, but its profit is also reduced. In addition, some carbon emission permits must still be purchased to avoid penalties for exceeding the EU-ETS carbon emission limits. However, if the price of the carbon emission allowance is too low, airlines will respond to the EU-ETS by simply purchasing a carbon emission allowance without altering their business operations
