 Aviation NOx emissions contribute to tropospheric ozone formation, which is linked to climate warming and adverse health effects. Modelling studies have quantified the relative impact of aviation NOx on O3 in large geographic regions but have not been able to attribute O3 formation to individual flights. This study applies the adjoint of the Global Chemistry Transport Model GeOS chemistry to assess the temporal and spatial variability in O3 production due to aviation NOx emissions, finding that Pacific aviation emissions could cause four to five times more tropospheric O3 per unit NOx than European or North American emissions. The study also computes the O3 burden attributable to 83,000 unique scheduled civil flights and finds that the top-ranked O3 producing flights normalized by fuel burn cause 157 times more normalized O3 formation than the bottom-ranked ones. These results show significant spatial and temporal heterogeneity in environmental impacts of aviation NOx emissions. This article was authored by Christopher K. Gilmore, Stephen R. H. Barrett, Jameen Koo and others. We are article.tv, links in the description below.