The measurement report by Tomsche et al. presents data on NH3 and NHx emissions from multiple types of fires. The emission factors were generated using high-resolution observations of NH3 and NH4+ conducted via airplane campaigns. There is only one potential major issue with the paper and I recommend publishing with minor revisions, presented below.

The only major issue is stated in line 100 - in field calibrations were inconsistent. It's not clear how much of an issue this is, but anytime a calibration fails in situ one is concerned about the quality of the data. The authors need to provide more detail so this concern can be alleviated. How confident are they that the measurements are accurate based on the laboratory calibration. 

In the introduction, line 59- it would be useful to provide more information to the reader on the differences of the Innsbruck instrument to the other instruments discussed in the paragraph. 

Section 2.2 - The authors should provide some evidence to support the statement on line 87 that the instrumental background was reduced to single digit ppb levels.

Line 111 - what are the implications of the 34% uncertainty in the NH4+ data on the final calculated emissions factors? Can that uncertainty somehow be propagated through?

Line 114 - There is potentially a lot of organic N compounds in burning emissions (e.g., Mace et al., 2003 Water-soluble organic nitrogen in Amazon Basin aerosols during the dry (biomass burning) and wet seasons). This could be contributing to the large amount of NH4+ measured early on in the fires. This needs to be stated very clearly throughout the paper as the authors have no way of knowing if this is an issue or not. 

Section 2.3 - is this the most commonly used method for calculating EFNH3? Also, why was the carbon fraction assumed to be 0.5? This should be justified. 

Conclusions on line 215 - If the discrepancy is based on the tailing and downwind data, then the authors could prove that by doing the calculation on their data excluding tailing and the downwind data. This would provide confidence in the conclusions. 

General comments

Tomsche et al. present a measurement report of NH₃ and NH₄⁺ during an aircraft campaign (FIREX-AQ 2019) and derive their emission factors (EF). They find higher EF_NH3 than laboratory measurements indicate for a variety of biomass burning conditions.

This work is topical due to the important role of reduced nitrogen in our atmosphere being increasingly recognized, significant due to the dearth of EFs from field measurements, and fits well within the scope of ACP.

Although the manuscript is concise, easy to read, and results are presented in a logically structured manner, there are some concerns that upon addressal may warrant its publication. These concerns, broadly regarding the lack of sufficient details and uncertainty analysis, are detailed below.

Specific comments

The EFs are reported as X ± Y g·kg⁻¹. It is unclear what the plus/minus value refers to. Is this 1σ or some other value? Does this reflect the variability across multiple transects alone, the uncertainties in variables and assumed values in the EF calculation, or both? This needs to be clearly described in the Methods. [Also, Reviewer #1’s comment on propagated uncertainties.]

An assumed carbon fraction of 0.5 for biomass may be conservatively off by ±10% (please also cite literature justifying this assumption). [Also noted by Reviewer #1]

How was the background mixing ratio estimated? What about during agricultural fires, where there may have been numerous such occurring around the same time and around the same place contributing to NH₃/NH₄⁺ in the sampled air; can elevated VMRs specific to the plume under consideration be reliably obtained?

Which plume transect segments were used in the analyses? Ideally, also plot the selected transects on the map showing location of fires (at least for the wildfires).

How were the classifications by fuel types obtained?

Lines 212-217: Since Gkatzelis et al. (2022) cited here is unpublished, unavailable as a preprint, and not made available at the time of the review, these lines cannot be reviewed. Suggest deleting or making Gkatzelis et al. (2022) available during the next round of revisions.

Suggest avoiding speculative statements such as: (Conclusions) “NH3 emissions were highest from fires of corn and rice residues, which may be caused by fertilization of these fields.” There was no analysis presented to make this claim (even if softened by “may”).

The primary finding is that EF_NH3 may be underestimated in laboratory studies. More details are required to develop confidence in the reader that this is the case. It may be that in the “real world conditions” there is burning/heating of duff and/or of the soil itself (NH₄⁺ and NH₄⁺ → NH₃) that is not considered in the lab among other possible factors. That these are insignificant aspects and that lab- and aircraft-derived EFs are equivalent but not equal needs to be demonstrated before the finding is presented as strongly as it is in the manuscript.

Technical corrections

Throughout the manuscript: ppb or ppbV and ppm or ppmV?

The supplementary figures and tables are important for the narrative. Suggest moving these to the main manuscript and not relegating to the supplement.

Figure 1: The error shading seems to consider only the average values (circles) and not their error ranges as well. Why? Please also describe what exactly the shading represents in the figure caption.

Suggestion: Due to wide range of values in Figs. 1 and 2b, suggestion to use log-log scale.