Abstract: With renewed interest in commercial supersonic transport (SST) aircraft due to increased demand for air travel, the environmental impacts on ozone and climate from proposed supersonic fleets need to be analyzed. In this study we have examined two such proposed fleets developed by MIT, flying at Mach 1.6 with a cruise ceiling at 17 km and representing either high or low economic growth. The high scenario burns 43.1 Tg of fuel with 0.39 Tg NOx and 0.14 Tg BC emission whereas the numbers for the low scenario are 9.6 Tg, 0.008 Tg and 0.03 Tg respectively. The UIUC analyses was done using the global climate chemistry model CESM2 – WACCM6 with model top ~140km with comprehensive troposphere-stratosphere-mesosphere-lower-thermosphere chemistry at a horizontal resolution of 0.9^o×1.25^o, and 70 vertical levels, compared to the GEOS-Chem simulation done by the MIT group. Our presentation will also include a comparison of the UIUC and MIT findings. The UIUC study indicates a global ozone column reduction by 0.33% and 0.06% respectively for the high and low scenarios, which can be attributed to the NOx emissions. For both the scenarios, the maximum ozone loss in Northern Hemisphere (NH) occurs during the summer and early fall (June-October), and during late fall (April-May) in the Southern Hemisphere (SH). Although fraction of SST emission is lower in SH compared to NH, atmospheric transport results in significant ozone loss in SH too. Although CO₂, SO₂, and soot emissions contribute to climate impacts, we find that the largest impacts are likely due to stratospheric ozone and water vapor perturbations. The UIUC net non-CO₂, non-contrail stratospheric-adjusted radiative forcing (climate impact) from the high and the low scenario was 14.7 mW/m² and 4.26 mW/m² respectively, indicating an overall warming effect of the order of 10% of that from modern subsonic aviation which grows non-linearly with fleet size.