## 2 Comparative Method
### Data and Application of the Scaling Approaches
#### 2.4.1 Application for In-Flight-Related OIs  
Trajectory-related OIs have been investigated by incorporating day-specific weather situations and atmospheric boundary conditions for one to four selected representative days. As only one comparable representative day is considered in all four studies, the detailed comparison is thus limited to this day. The target flight plan is defined by all flights originating or departing from the ECAC area performed with Airbus or Boeing passenger aircraft and with a distance of at least 500 km. This covers 25.3% of the global flight plan ASK on the selected day and 87.8% of all European flights. Reference flight plans vary significantly for the individual studies (see Appendix A). KPIs of the comparison are set to F-ATR100, which is derived from ATR20 by applying conversion factors determined in [PERSON] et al. [67], and DOC. Since the considered mission adjustments are limited to the flight itself without changing aircraft assignments or OD pairs, we assume that passenger capacities and ticket prices do not change with the OI implementation. The scaling is performed as follows: Based on the measure-specific reference flight plan, climate mitigation potentials in terms of ATR100 are scaled to the target flight plan of the selected representative day. CO\({}_{2}\)-Eqs for the selected representative day are estimated with algorithmic climate change functions (aCCFs) [67; 68], which have been assessed for the full target flight plan. On this basis, different application scopes of the investigated OIs can be modeled, e.g., an application of LOSL for all long-range flights to or from the ECAC area or an application of CLIM for North Atlantic flights only. However, an implementation of LOSL is assumed to be suitable for long-distance flights only as shorter Intra-European missions are typically performed at lower flight altitudes and are expected to be addressed by optimized routing concepts as covered by the OIs FREE and WIND. Resulting changes in DOC are scaled based on the traffic size, namely ASK.  
The comparison of network-related OIs is performed based on all flights covered by European airlines, annually aggregated for 2018. The results from the individual case studies are scaled to a target flight plan consisting of all flights performed by these airlines focusing on three airline types, namely primary hub-and-spoke (H&S) airlines, secondary H&S airlines, and low-cost carriers (LCC). Regional airlines are excluded from the considerations. The resulting target flight plan covers 19.6% of all global ASK in 2018 and 69.4% of all flights from and to Europe. As NETW has been assessed individually for one representative airline per category, scaling is performed in two steps: First, mitigation potentials per representative airline are scaled to all airlines of the same category in accordance with their respective fleet size. By doing so, we assume that the bigger an airline fleet is, the higher optimization potentials can be achieved. Second, the climate mitigation potential per airline type is scaled according to the respective ASK and average CO\({}_{2}\)-Eq per airline type. By contrast, an individual scaling for the ISOC results is performed, including a matching based on flight characteristics. CO\({}_{2}\)-Eqs are calculated with the regression formulas provided by [PERSON] et al. [66]. To assess the stakeholder impact, DOC and profit are considered. The consideration of profits is required for the NETW OI as network adjustments lead to changes in served missions, frequencies, and payloads thus influencing captured demand and revenue. The stakeholder analysis of ISOC is focused on DOC, while resulting changes in profit can only be indicated qualitatively due to limited data availability.