see comments in attached file

Review of "A high-resolution Global Aviation emissions Inventory based on ADS-B (GAIA) for 2019–2021" by Teoh et al.

This manuscript presents a new aviation emissions data based on individual flight level data and models of engine performance. Most of the technical details are in the supplement, and summary analysis is presented in the main manuscript. 

The manuscript is a good description and analysis of an important new dataset for aviation emissions covering the period 2019-2021, pre, beginning and mid pandemic. The analysis in the manuscript is well presented. It should be publishable with minor revisions. I think some of the analysis could be presented a little better with some more figures (in addition to tables) as noted below. The supplement seems correct and comprehensive. The data (low time resolution) has been posted to an available archive. 

Specific comments: 

Page 2, L31: where does the 1034 Tg number come from (reference?)

Page 5, L140: How does the -8% lower comparison at major airports mesh with +15% to +20% globally?

Page 5, L150: can you say what the default is and what the modifications are briefly?

Page 11, L255: see note on table 4. I suggest making a histogram that makes clear the differences between consumption and distance (and emissions) by region…

Page 11, L252: for fleet compostition, higher fuel use rate per km is due to more narrow body aircraft?

Page 11, L285: maybe figure 2c could be in percent?

Page 13, L290: suggest that the percent values of distance, fuel and emissions by region be made into a histogram (grouped by region) to make deviations from say % distance travelled evident.

Page 15, L308: I though short haul were less efficient (kg/km) per unit distance? (E.g. discussing China above) Or is that not the case? Please clarify.

Page 20, L409: You have Fuel consumption per passenger-km: is that the same as gross fuel consumption? Presumably the rerouting is to save fuel, so the variance in fuel used should be smaller than distance? Would be interesting maybe to state total fuel per flight on this route and how much it varies (more or less than distance).