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Aviation is a unique anthropogenic source with four-dimensional varying emissions, peaking at cruise altitudes (9-12km). Aircraft emission budgets in the upper troposphere lower stratosphere region and their potential impacts on upper troposphere and surface air quality are not well understood. Our key objective is to use chemical transport models (with prescribed meteorology) to predict aircraft emissions impacts on the troposphere and surface air quality. We quantified the importance of including full-flight intercontinental emissions and increased horizontal grid resolution. The full-flight aviation emissions in the Northern Hemisphere contributed similar to 1.3% (mean, min-max: 0.46, 0.3-0.5ppbv) and 0.2% (0.013, 0.004-0.02g/m(3)) of total O-3 and PM2.5 concentrations at the surface, with Europe showing slightly higher impacts (1.9% (O-3 0.69, 0.5-0.85ppbv) and 0.5% (PM2.5 0.03, 0.01-0.05g/m(3))) than North America (NA) and East Asia. We computed seasonal aviation-attributable mass flux vertical profiles and aviation perturbations along isentropic surfaces to quantify the transport of cruise altitude emissions at the hemispheric scale. The comparison of coarse (108x108km(2)) and fine (36x36km(2)) grid resolutions in NA showed similar to 70 times and similar to 13 times higher aviation impacts for O-3 and PM2.5 in coarser domain. These differences are mainly due to the inability of the coarse resolution simulation to capture nonlinearities in chemical processes near airport locations and other urban areas. Future global studies quantifying aircraft contributions should consider model resolution and perhaps use finer scales near major aviation source regions.

Plain Language Summary In the Northern hemisphere, aircraft emissions contribute similar to 1.3 % and 0.2 % of total O-3 and PM2.5 concentrations at the surface. Incorporating full-flight aircraft emissions at a fine resolution improved model estimates of NO2 by similar to 5-11% when compared to field campaign observations in upper troposphere lower stratosphere region. Coarse resolution showed similar to 70 times and similar to 13 times higher aviation impacts for O-3 and PM2.5 when compared to fine resolution over North America. We attribute these overestimates to physical and chemical processes in the choice of grid resolution, as well as due to intercontinental transport of pollution.