The effect of future subsonic aircraft emissions on the chemical composition of the atmosphere is investigated by means of the coupled dynamic-chemical circulation model ECHAM3/CHEM. Present (1992) and future (2015 and 2050) atmospheric compositions are simulated with three sets of time slice experiments. Expected changes of the sea surface temperatures (SST), surface emissions of CFCs, greenhouse gases (GHG), and NOx(=NO+NO2) are prescribed. Model results show future increases in NOx and O3 due to aircraft NOx emissions, which scale almost linearly with the magnitude of the emission. The calculated climate change reduces the NOx concentration as well as its increase due to aircraft emissions by more than 10% at flight altitude in 2015. However, the aircraft induced ozone perturbation decreases only slightly when climate change is regarded. ¿ 1999 American Geophysical Union