Source: https://ccep.crawford.anu.edu.au/sites/default/files/publication/ccep_crawford_anu_edu_au/2018-11/csereklyei_z._and_stern_di_2018_flying_more_efficiently-joint_impacts_of_fuel_prices_capital_costs_and_fleet_size_on_airline_fleet_fuel_economy_ccep_wp_1810_anu_0.pdf