Analytical Models of Flight Fuel Consumption and Non-CO₂ Emissions as a Function of Aircraft Capacity

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Montlaur et al. present and analyze parametric models for estimating fuel consumption and subsequent emissions (CO2, NOx, and SOx). They summarize factors that make net-zero aviation emissions difficult to achieve by 2050. Fuel consumption was calculated using EUROCONTROL's IMPACT platform, considering historical data and flight parameters to test the model, they case-study Spanish air traffic in one day. Emissions were analyzed relative to flight distance and ASK. A low percentage of long-haul flights generated a disproportionate share of total ASK and CO2 emissions. Recent works are ignored (Zhang 2025, Pagoni 2017). Similarities and differences must be compared in order to highlight the original contribution. The manuscript is a hard major revise.
Some suggestions to improve the manuscript are listed below.

Minor
The markers in Fig 3 need to be smaller and different so when they overlap one can tell the difference.

Major
Some limitations observed are listed below and should be included in the manuscript to warn the reader.
The selected models primarily rely on flight distance and available seat numbers, potentially oversimplifying the complex processes influencing emissions, such as aircraft type, engine efficiency, and operational conditions.
The study concentrates on the most used aircraft in 2022, which may limit the applicability of the models to less common or newer aircraft, potentially reducing their generalizability. A suggestion could be analyzing the data as part of the whole group to establish the percentage of total flights for the same year.
While non-CO2 emissions like NOx are modeled, the complexity of their climate impacts and interactions (such as contrail formation and cirrus cloud effects) are not fully captured, possibly underestimating total environmental impact.
The authors present goodness-of-fit statistics but lack extensive validation or comparison with real-world emission measurements. It could strengthen the credibility of the models.
The manuscript does not address the uncertainties inherent in the modeling approach or propose methods for future refinement, which is crucial for practical applications.

There is a pre print (Zhang, 2024) that is very similar but applied to Chinese flight records.
https://arxiv.org/html/2409.05429v2

The complete reference is below.

***

Zhang, et al. A comprehensive framework for estimating aircraft fuel consumption based on flight trajectories. Transportation Research Part E: Logistics and Transportation Review. 203, 2025, 104339
https://doi.org/10.1016/j.tre.2025.104339

Pagoni; Psaraki-Kalouptsidi. Calculation of aircraft fuel consumption and CO2 emissions based on path profile estimation by clustering and registration,
Transportation Research Part D: Transport and Environment, 54, 2017, 172-190, https://doi.org/10.1016/j.trd.2017.05.006.

Comments on the Quality of English Language

English

Some sentences are long and complex, preventing a clear understanding. I suggest breaking them into shorter sentences to improve readability.
Sentences like “the dispersion of the results obtained is so high that it became impossible to find a single model fitting for all distances” can be shortned for clarity, “the high dispersion of results made it impossible to develop a single model that fits all distances”
Similar issues with sentences like “it can be seen by looking at Figure 5 that the error of the analytical fitting is higher in the range of long-haul distance with a low number of seats,” which could be clearer as “Figure 5 shows that the analytical fit error is higher for long-haul distances with few seats.”
There are some missing commas before conjunctions in complex sentences.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article explores the potential application of an analytical model to determine fuel consumption and emissions from combustion in the aircraft industry. From the perspective of assessing the industry's current development, the article is interesting because it identifies trends in efficiency and environmental impact.

I have the following comments and notes on the article.

 

1. The introduction provides a critical analysis of the mechanisms used to determine carbon and non-carbon emissions to date, highlighting the impact of industry on the extent of climate change. This section should conclude with a clearly defined objective for the study and the tasks necessary to achieve it. It should also indicate things that have not been taken into account in previous similar developments.
2. Section 2.3: Usually the proportional emission factor is presented as g/kg fuel spent or g/kWh energy. Please specify.
3. When referring to fuel consumption in terms of passengers and kilometers, it should be called "specific fuel consumption.";
4. Why does the specific fuel consumption at different available seats behave differently? (Figure 2)
5. The conclusion section should be improved by adding information about the model's accuracy limitations. Additionally, the possibility of using conventional and other types of fuels, such as hydrogen, in jet engines could be discussed.

Comments on the Quality of English Language

The English language is quite fine. Only minor adjustments are needed.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have submitted a satisfactorily revised version. I recommend the manuscript for publication.