Fuel Tankering: Economic Benefits and Environmental Impact for Flights Up to 1500 NM (Full Tankering) and 2500 NM (Partial Tankering)

Round 1

Reviewer 1 Report

This is an interesting topic and a nicely written paper, with potentially important implications. It presents the method to assess the likely impact of fuel tankering on both airline economics and the environment.

The method for estimating the effects for a single flight is solid and well described, with some particularly nice insights and graphs (esp. Figures 9, 10 and 12). The assumptions are valid and reference to real-life values is one of the key values added of the paper (particularly concerning airline-negotiated fuel prices at different airports and profit threshold per flight).

It should be stressed that fuel costs as % of airline operating cost are highly variable over time and over different airline business models, and can be much higher (and sometimes somewhat lower) than the mentioned 17-25% range, especially for low-fare carriers and in particular in times of high oil/fuel price.

The results, especially for what concerns estimated annual effects, are heavily dependent upon the assumed load factor and the fuel price. To that end, a fairly simple sensitivity analysis could be quite beneficial for the paper, showing how the results would change if a different average load factor is assumed (e.g. 90% - which was quite typical for low-fare carriers prior to Covid era, or 70%, which is also a sensible/realistic scenario). Low-fare carriers constitute about 30% of IFR flights in ECAC area, are arguably more cost-conscious than legacy carriers, and their routes typically fit quite nicely into the current scope of analysis, in terms of distance, so might be worthwhile to have a closer look into this market segment. Similarly, it might be interesting to see what the results would look like if fuel was e.g. 20% (or 50%) more or less expensive compared to the base case studied (Jet fuel price), as we have many times witnessed quite sharp changes in fuel price over relatively short period (as Figure 11 already shows).

With regard to extrapolation from June 2018 to entire year, it should be briefly discussed if, in which way and to what extent such methodological choice may affect the results, e.g. in terms of representativeness of June traffic structure across the year, etc.

The estimate of annual net saving due to tankering (265M EUR) should be reported together with the fuel price assumed in the analyses (e.g. average jet fuel price for June 2018). Here the aforementioned sensitivity analysis with regard to the fuel price would be extremely helpful and could indicate the range of savings under different fuel price scenarios (instead of having only a point estimate).

The estimated extra CO2 emission due to possible tankering should be put into perspective, e.g. as % increase vs. base case (e.g. no-tankering scenario). In other words, stating that tankering practices might add X% on top of already existing emissions.

On p5 authors state the airline-reported percentages of 15% each for full tankering and partial tankering, which I assume relates to the incidence of flights exercising such practices. This should be rephrased to make it straightforwardly clear.

Figure 14 title should read something like: “% of flights which could exercise fuel tankering (and save money by doing so), per distance flown”.

Reference 11 is missing the author(s).

Author Response

Thank you for you review; Please see the attachment.

Laurent

Author Response File: Author Response.docx

Reviewer 2 Report

This paper addresses an interesting topic not particularly investigated in the literature, fuel tankering in aviation. Although the subject is worthy of investigation and the methodological approach used in the article is correct, the work needs, in my opinion, to be improved in some of its parts before it can be considered for publication.

The most important gaps are in my opinion two. The first is the lack of a solid base of reference that motivates the study, from the scientific point of view and not only from the application one. The introduction is too concise, the bibliographical references are few and the work lacks a framework in the research landscape on aviation, fuel efficiency and CO2 emissions. The second problem is a structuring of the article that is not entirely clear and of little support in reading and understanding the objectives, methods, and results.

Concerning the first issue, it is true that the literature on the specific topic of fuel tankering is very poor, as the authors rightly point out. But it is equally true that there is a large and articulate body of research on the topics of aviation fuel consumption and, especially, on the topic of CO2 emissions. Given that the authors have highlighted that, among the various reasons that push companies to adopt the practice of fuel tankering, the most relevant are those related to ground handling aspects at the destination airport (costs, need to reduce turnaround time, etc...), I therefore suggest expanding and reinforcing the introduction considering, just as a suggestion, the following works:

• Nikoleris, T., Gupta, G., Kistler, M., 2011. Detailed estimation of fuel consumption and emissions during aircraft taxi operations at Dallas/Fort Worth international airport. Transport. Res. Part D 16, 302–308.
• Daley, B., Preston, H., 2009. Aviation and climate change: assessment of policy options. In: Gössling, Upham (Eds.), Climate Change and Aviation. Issues, Challenges and Solutions, pp. 347–372.
• Postorino, M. N., Mantecchini, L., & Paganelli, F. (2019). Improving taxi-out operations at city airports to reduce CO2 emissions. Transport Policy, 80, 167-176.
• Postorino, M. N., Mantecchini, L., & Paganelli, F. (2017). Green airport investments to mitigate externalities: Procedural and technological strategies. In Sustainable Entrepreneurship and Investments in the Green Economy (pp. 231-256). IGI Global.

Regarding the second problem, in my opinion the current division into paragraphs does not allow to highlight the sequence of hypothesis, methodological approach, case study, commentary of results and conclusions. I suggest the following changes:

• Paragraph 2 should be written in text form and not as a bulleted list.
• Paragraph 4 should also not be presented as a bulleted list. Also, I think it is good to break it up in this way: from 4.1 to 4.3 a paragraph containing the methodological approach; from 4.5 to 4.8 another one containing the results and related discussion.
• Section 4.3 (study limitations) should be included in the conclusions, which should however be expanded by adding a number of considerations about future potential applications of the results highlighted in the work.

Other remarks:

• The content of Fig. 12 is very interesting (fuel price differences at various European airports). However, its interpretation is not unambiguous and elementary (in fact, it is not clear whether the color refers to the average of the differences between a certain airport and the destinations with which it is connected). I would suggest integrating the figure with a table showing some specific data on routes for which information is available (e.g. those indicated in the text at the bottom of page 12).
• The table on page 14 is uncaptioned and should be put in the format provided by the layout. In addition, the sources that allowed the calculation of extra CO2 emissions (emission factors) and their economic quantifications should be indicated. This is an important step in the work and must be well argued.
• On page 8 Figure 4 is not mentioned in the text, perhaps Figure 5 is mentioned twice.

Author Response

Thank you for your review; Please see the attachment.

Laurent

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript and content of the article are very well prepared. The paper focuses on the practice of refueling in the context of reducing aviation emissions from the combustion of fuel needed to perform each flight. The topic of the study and the discussion on it is very actual.

The purpose of the study at ECAC (the European Civil Aviation Conference) level is to estimate the extent of the environmental impacts of refueling, due to the demand for decarbonization of transport.

The authors used the relevant methodology for solving the problem (STEP 1-4), with the support of Aircraft performance based on EUROCONTROL BADA (Base of Aircraft Data) model, and Fuel prices negotiated at 140 airports in ECAC from 2 major airlines, etc. The authors defined the limits of the study.

While maintaining flight safety, the priority of air carriers is usually their economic efficiency, reducing operating costs. The environmental impacts of aviation are secondary. The question remains to find tools to change thinking and corporate culture so that, while maintaining flight safety, the environmental impact of air travel from a particular flight becomes a priority over reducing air carrier costs. The question for discussion may be whether, for example, passenger charges for the "carbon footprint" of aircraft can offset the costs of air carriers and encourage a change in their thinking.

Due to market freedom and competition in the fuel market, we cannot eliminate the regional differences between departure and arrival airports. As a former pilot and now a passenger, I am writing against air transport, which will increase the price of the ticket but perceives it as a tax on this type of transport. If I do not accept this, I have to choose another mode of transport that can be more environmentally friendly. Air transport will compete with high-speed trains, especially on short distances, etc. The main benefits of air transport, even with a possible surcharge for the "carbon footprint" compared to other modes of transport, plus the adopted changes in refueling described in the article, I expect on medium and long-haul routes. The publication of the results of studies, comparative analyzes, and the sharing of experiences in an expert discussion with the aim of raising awareness of the considerable environmental impact of "fuel tankering" are welcome.

I have no significant comments. I recommend the article for publication in a professional and research discussion on this issue.

Minor comment:
For the first time, the abbreviation ECAC is used in the abstract, without the full text to identify "the European Civil Aviation Conference".

 

Author Response

Thank you for your review; Please see the attachment.

Laurent

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The manuscript has been somewhat improved following the first round of review. I still have a few fairly minor suggestions for quick further improvement of the manuscript which I attach. On top of those, I spotted a technical issue with newly added text on pages 7 and 8. It says, e.g. "350 FL", or "290 FL", whereas the aviation standard is to write "FL 350" and "FL 290". Please make sure this is corrected throuthout the text.

Comments for author File: Comments.docx

Author Response

Thank you for your review; see responses in the document uploaded.

Author Response File: Author Response.docx

Reviewer 2 Report

The comments and suggestions made in the first round of review were largely accepted by the authors. As far as I am concerned, I am still perplexed about the massive use of bullet points in sections 2 and 4, which is not so frequent in the narrative part of scientific articles. But this is not a relevant problem.
The literature review has been slightly expanded (I appreciate the inclusion of the ICAO document which, although dated, is very relevant), I would have preferred a broader framework (in addition to the specific topic of fuel tankering) since the addition of additional references would have better consolidated the starting point of the work, while expanding the range of potential readers, as I had indicated during the first round.
As far as I am concerned the work has been significantly improved. If the authors do not intend to make further changes I suggest a final check for minor errors.

Author Response

Thank you for your review see response in document uploaded.

Author Response File: Author Response.docx