## 3 Results: Comparing Different Operational Mitigation Measures in Aviation
### Comparison across Measure Types  
Figure 10 displays a final qualitative comparison of the results with respect to the mitigation potentials, stakeholder impacts, and maturities of the investigated OIs. In this context, economic and operational effects for the air transport system are divided by impacted stakeholders, including airlines, airports, ANSPs and passengers. Indirect effects, such as increasing prices for airlines due to higher costs for airports or increased ticket prices for passengers due to higher costs for airlines, are excluded from this analysis. A direct quantitative comparison is so far only possible within similar categories as different assessment methods and boundary conditions have been applied per category. For the semi-qualitative comparison of all considered OIs, we need to differentiate between  
Figure 10: Overview and comparison of achieved results for individual OIs. Climate mitigation potential is indicated semi-quantitatively from very high (\(\bullet\bullet\bullet\bullet\bullet\bullet\bullet\)) to very low (\(\blacklozenge\)\(\blacklozenge\)\(\blacklozenge\)) absolute climate mitigation potentials. Stakeholder impact is given as strongly negative (- - -), negative (- -), slightly negative (-), slightly positive (+), and positive (+ +). Figure 9: Absolute CO\({}_{2}\) emissions and their reduction by implementing the different OIs (**left**) and climate mitigation potential (ATR100) per considered ground-related OI (**right**) generalized for all airports in the ECAC area. relative and absolute mitigation potentials. On the one hand, we see very high relative mitigation potentials for ground-related OIs in comparison to the in-flight OIs. Also, we observe high mitigation potentials for climate-optimized routing and climate-optimized ISO, whereas we find lower relative potentials for free- and wind-optimized routing and strategic network planning incorporating climate effects. On the other hand, the absolute reduction of climate effects in ATR100 is significantly higher for in-flight measures compared to on-ground improvements. This can be illustrated by the CO\({}_{2}\) emissions caused by the different target flight plans and target airports: We observe 150-200 Gt of CO\({}_{2}\) emissions for the annual flight plan of the network-related OIs and 440 Mt of CO\({}_{2}\) for the target flight plan of the selected December day investigated for the trajectory-related OIs. In comparison, the overall CO\({}_{2}\) emissions of all European airports resulting from taxiing, ground transport, and buildings are estimated to be 5 Mt annually. Moreover, we see average CO\({}_{2}\)-Eq between 3 and 4 for the in-flight climate impact, thus we estimate absolute mitigation potentials of in-flight OIs to be significantly larger. Implementation of OIs is limited through the associated impact on the different stakeholders of the air transport system. For instance, as OIs FREE and WIND increase efficiency, cost for operators and travel times for passengers can be reduced. However, an upgraded infrastructure for advanced wind and weather services and ATC modernization will be required, associated with additional investments. ATC workload is expected to increase in the context of wind-optimized flight planning, possibly influencing delays and air navigation charges. In addition, LOSL and CLIM are associated with longer flight times and increased fuel consumption leading to higher DOC. Passenger acceptance is expected to decrease due to longer travel times [76]. The same holds true for network-related OIs: deviation from economically efficient operations towards more climate-friendly concepts increases costs and reduces profits for airlines. Potentially longer detours, travel times, more intermediate stops, and number of flights needed for the same OD combination result in reduced passenger acceptance [76]. Moreover, higher fuel consumption, flight times, additional starts, and landings as well as adjusted frequencies affect the operating cost and profit of the operators.