Studies on the potential of Intermediate Stop Operations for today’s airlines

This study shows the short-term potential of Intermediate Stop Operations (ISO) from an individual airline’s perspective. The concept of ISO aims at reducing the fuel consumption on long-haul flights by refueling the aircraft at an intermediate airport. The reduction of the fuel weight at take-off leads to an increase in the overall fuel efficiency. Thus, on longhaul flights with two legs, aircraft with a shorter design range can be operated. The potential of ISO is analyzed by modeling the airlines’ operations based on the route and fleet structure. The substitution of long-haul aircraft by existing, short or medium range aircraft is considered, assuming that flights are performed in two stages. Corresponding block fuel and travel time values are calculated based on EUROCONTROL’s BADA data to identify the most fuel efficient operating mode and airport. Also a model for the Cash Operating Cost of an airline is set up and applied to calculate the actual cost benefit induced by ISO. The changes in the airline’s fleet utilization and schedule feasibility due to longer flight-times are considered in the assessment of the ISO concept. The identified intermediate airports are clustered and their suitability as dedicated ISO hubs is investigated. It is found that an exemplary European hub airline can save up to 11,400 t per month under real operational conditions, corresponding to 430,000 t CO2 per year. This amount can be even multiplied up to tenfold by applying different cabin comfort levels. Whereas the theoretic fuel saving potential is high even for existing aircraft, the study also reveals that with a current fuel price of about 0.97 USD/kg the cost savings for airlines due to ISO are still little. Anyhow, the attractiveness of the concept grows when the fuel price increases or additional environmental charges are imposed