The paper is relevant to the area of aircraft routing and addresses the choice between multiple optimal routes dependent on a range of objectives.  As such this is not a major change to routing strategies, but rather a next step in an evolving process. This means that the novelty of the approach lies in applying an established algorithm to a new setting. The advance this affords allows the previously defined AirTraf model to be used in a different and more integrated way. The method described is mostly clear, but some of the assumptions supporting the use of AirTraf in contrail avoidance are not properly justified, given research results previously published on the nature of super saturated icy regions. This is further explored in the more detailed file that is attached below.

Results are somewhat limited by the use of a single month, which when looking at climatic conditions provides a narrower range of possible variable value combinations than is most useful. However, conclusions across this reduced timeframe given the other model assumptions are supported by the research that has been completed. Given the reliance of the results on a combination of different models and the limited explanation in this paper of the climate inputs and methods for fuel use calculation, it would be difficult to reproduce results from this work alone, but taken alongside previous research and given the limited access to models available, replication of some of the results could be possible. 

The work is properly referenced and the need for the model is justified, with the paper title including all necessary detail. The abstract is concise and reflects the paper content, but could be better worded (see attached comments). The main structure of the paper is good, but there are occasions where order within sections would be improved by small changes. The language and grammar of the paper need minor corrections, which have been noted in the attached comments. Clear definitions of formulae, symbols and abbreviations are, however, all present in the paper.

This manuscript presents the SolFinder tool, a multi-criteria decision making (MCDM) application designed to identify eco-efficient aircraft trajectories. It accomplishes this by solving a bi-objective optimization problem aimed at minimizing both climate impact and operating costs. The development of the MCDM tool, along with the results it yields, appears to be of interest to the readership of Geoscientific Model Development. Overall, the manuscript is clearly written and generally well-structured. I recommend only minor revisions to address the points listed below before accepting it for publication.

1. The terms "Pareto-optimal solutions" and "Pareto optimal solutions" are both accepted in the literature; however, consistency within your manuscript would enhance its presentation. Please choose one format and use it uniformly throughout the paper.
2. On line 156, the authors write, “If the VIKOR method identifies more than one recommended solution, i.e., the solutions pv (v = 1,2,...,M) are equally recommended, the model selects the one with the minimum value of the objective function assigned to the lowest weight wn”, justify why it opts for the solution with the minimum value of the objective function corresponding to the lowest weight. Would it be more logical for the final selection to be based on the objective with the highest weight since it represents the most important criterion?
3. Figure 2 could be enhanced for clarity and visual appeal. Firstly, it would be beneficial to use a single color and symbol to denote the Pareto-optimal solutions—currently, there is a mix of red dots and gray crosses, which can be confusing. Secondly, adopt a consistent color and symbol for the solutions recommended by VIKOR, which are presently indicated by both red dots and green crosses. Lastly, I suggest using a distinctly different color and symbol to highlight the final selected solution in Figure 2d. A blue star or another distinctive marker could be effective in clearly indicating the chosen solution to the audience.
4. Ensure consistency in your manuscript by using either "decision-maker" or "decision maker" throughout the paper.
5. The manuscript mentions that decision-makers must configure the values for gamma (γ) and weights when using the VIKOR method implemented within SolFinder. While determining weights may be more intuitive for decision-makers, selecting an appropriate gamma (γ) value could pose a challenge for those less familiar with the subject of the MCDM or VIKOR method. I recommend that the authors include a brief, accessible explanation of how varying gamma (γ) values influence the outcomes. For example, elucidate the implications of a gamma (γ) value near 1 versus one closer to 0, and clearly state the default gamma value used in your program, such as 0.5, if applicable. This explanation would benefit both the paper and the SolFinder tool itself, leveraging insights from your good sensitivity analyses.