This manuscript includes a simulation study of terrestrial gamma-ray flashes (TGFs), one of the high-energy atmospheric phenomena associated with thunderstorms. TGFs have been detected by space-borne instruments, but recently, airborne observations of TGFs are becoming of greater importance. This study are aiming at verifying the detectability of TGF-related high-energy particles by airborne observations. The manuscript is well organized. On the other hand, I found that several important previous studies are completely missed, and furthermore, the obtained simulation results are not well exploited. Therefore, we recommend a major revision before the decision.

Major issues

There are previous simulation studies on high-energy atmospheric phenomena, and some of them should be cited. Furthermore, the present result should be compared to the previous studies in order to highlight the novelty of the present work. If comparison is impossible, the authors should justify it. I list the references below.

Electrons and photons:

• Pallu, M., Celestin, S., Hazem, Y., Trompier, F., & Patton, G. (2023). XStorm: A new gamma ray spectrometer for detection of close proximity gamma ray glows and TGFs. Journal of Geophysical Research: Atmospheres, 128, e2023JD039180. https://doi.org/10.1029/2023JD039180
• Sarria, D., Østgaard, N., Marisaldi, M., Lehtinen, N., & Mezentsev, A. (2023). Library of simulated gamma-ray glows and application to previous airborne observations. Journal of Geophysical Research: Atmospheres, 128, e2022JD037956. https://doi.org/10.1029/2022JD037956 (This paper is for gamma-ray glows, but I think it is worth mentioning in the manuscript.)
• Sarria, D., Rutjes, C., Diniz, G., Luque, A., Ihaddadene, K. M. A., Dwyer, J. R., Østgaard, N., Skeltved, A. B., Ferreira, I. S., and Ebert, U.: Evaluation of Monte Carlo tools for high-energy atmospheric physics II: relativistic runaway electron avalanches, Geosci. Model Dev., 11, 4515–4535, https://doi.org/10.5194/gmd-11-4515-2018, 2018
• Rutjes, C., Sarria, D., Skeltved, A. B., Luque, A., Diniz, G., Østgaard, N., and Ebert, U.: Evaluation of Monte Carlo tools for high energy atmospheric physics, Geosci. Model Dev., 9, 3961–3974, https://doi.org/10.5194/gmd-9-3961-2016, 2016

Neutrons

• Rutjes, C., Diniz, G., Ferreira, I. S., & Ebert, U. (2017). TGF afterglows: A new radiation mechanism from thunderstorms. Geophysical Research Letters, 44, 10,702–10,712. https://doi.org/10.1002/2017GL075552
• Pablo G. Ortega (2020), Isotope production in thunderstorms, Journal of Atmospheric and Solar-Terrestrial Physics, 208, 105349, https://doi.org/10.1016/j.jastp.2020.105349.
• Wada, Y., Enoto, T., Nakazawa, K., Odaka, H., Furuta, Y., & Tsuchiya, H. (2020). Photonuclear reactions in lightning: 1. Verification and modeling of reaction and propagation processes. Journal of Geophysical Research: Atmospheres, 125, e2020JD033193. https://doi.org/10.1029/2020JD033193

The authors show the simulation results of gamma rays, electrons, and neutrons by two-dimensional contours and energy spectra. In my opinion, however, the presentation is not enough, and further analysis is needed. For example, the authors claim that the distribution of gamma rays and electrons are different, but the difference is not obvious in the plots and I suggest the authors make a ratio plot of Figure 1 and Figure 3. If the authors would like to discuss the hardness ratio of the spectra, the hardness should be calculated and plotted.

Also, the main focus of this manuscript is the detectability of TGFs by airborne detectors. To clearly show the results aligning with this purpose, I suggest making figures to show the detectability of TGFs, with a function of TGF brightness (the initial number of electrons) and the effective area of a detector for each altitude and each particle type. See also Figure 23 in Pallu et al. 2023 (listed above).

Minor issues

• Some citations are not correctly formatted (for example, Fishman et al., 1994 at Line 16 in Page 1).
• L.77, P.3: Please check the citation (Oceanic and Administration, 2023)
• The authors use the primary electron spectrum obtained by Dwyer 2011, but I cannot find Dwyer 2011 in the reference list. Because the primary information is quite important in this study, I recommend showing the function of the energy spectrum or a plot.
• As MCNP6 is not widely used in this community (as far as I know), the authors should explain what physics is included in this code. Especially, the propagation process of electrons depends on the Monte-Carlo code, and its verification has been intensively performed by Rutjest et al. 2016 and Sarrial et al. 2018 (both are listed above). Also, the cross-section of photonuclear reactions is very important for neutron production and the authors should explain which database is used.
• L.100 P4: previouslz -> previously
• L.114, P.4: Citation is not correct.
• Figure 1: lowercase is used in the figure, but the caption uses uppercase.
• Figure 2 and the main text; the line feature at 511 keV should be carefully analyzed because the peak intensity of the line highly depends on the spectrum binning. Also, the authors discuss the important of the annihilation line, but the discussion remains qualitative. I recommend the authors qualitatively evaluate the intensity of the 511-keV line. The line intensity is often evaluated by equivalent width.
• Subsection 3.3: Are absorption processes of neutrons in the atmosphere included?
• L.180: recommend adding "currently"
• L.194, P.10: Tran15 -> Tran et al. 2015
• L.241, P.11: According to the policy of the journal, upon request is not favorable unless the authors have a reason. Please consider putting the raw data in a public repository. https://www.atmospheric-measurement-techniques.net/policies/data_policy.html

This paper reports simulations of terrestrial gamma-ray flashes to assess the potential for observations at aircraft and balloon altitude.

In my opinion, the paper is not particularly novel, reproducing something which has already been extensively explored in the past two decades in many papers, especially concerning photons. However, the focus on aircraft and balloon observations is somehow timely, given the recent aircraft campaign results.

The simulations are carried out with NCMP, a simulation tool which, to my knowledge, has not been used in this field before. However, the authors do not compare quantitatively their results with what already published in literature, which casts criticism on the applicability of their results. In addition, although the paper is in general clearly written, there are some missing references and incomplete sentences that must be fixed.

In the end, I think that the paper can be published only after major revision. The main points to be addressed are reported in the following, and are further detailed in the comments in the annotated pdf.

Major comments:

- assumptions for the simulations. An electron vertical beam is considered, with a fluence larger than observed on average from space, and no intrinsic beam width is considered. I think that these assumptions do not reflect the true phenomenology of TGFs coming from observations, therefore limiting the applicability of the presented results.

- lack of comparison with previous results. The authors should compare quantitatively their results with available literature (ion particular the Hansen et al., 2013, paper concerning photons, the Dwyer paper concerning electrons, and the Carlson paper concerning neutrons), address and discuss the discrepancies.

- the recent ALOFT results from aircraft are published and should be discussed. I mean: Østgaard et al., 2024, Nature; Marisaldi et al., 2024, Nature, and Bjørge-Engeland et al., 2024, GRL.