Model studies of the impact of aircraft emissions on atmospheric ozone, and on the methane lifetime have been performed, using a global 3-D CTM (The Oslo CTM1). The calculated changes in the global distribution of ozone and methane have been used to calculate Radiative Forcing (RF) of the current and future fleets (2015 and 2050) of subsonic aircraft. The calculations show that ozone perturbation from aircraft emission occur predominantly in the Northern Hemisphere at mid and high latitudes. Masimum increase in ozone is found in the upper trosphere in the 10 to 12 km height region. The annual average future increases in the region of maximum increase, is estimated to be approximately 12 ppb in 2015. Scenarios for NO_x emissions in 2050 are less certain, however; calculations give a near linear increase in global ozone perturbation for increasing NO_x in the future over the range of NO_x emissions assumed to by realistic until 2050. Calculations with NO_x emissions assumed to be realistic until 2050. Calculations with NO_x emissions well beyond this range (50% higher than the high NO_x emission) showed non-linear ozone response with less ozone increase per NO_x increase than in the cases with lower NO_x emission from aircraft. There is a a reduction in the methane lifetime due to enhanced OH from NO_x emissions. The change in the global methane lifetime is estimated to be -1.3% in 1992 from aircraft emissions, increasing to -3.9% in 2050. Estimates of RF from CH₄ and O₃ due to aircraft emissions are of opposite sign and of similar magnitude, which makes it difficult to give reliable estimates of the net impact. The regional patterns in RF for the two compounds are however highly different. It is therefore likely that the radiative impact from NO_x emissions could be larger than what can be obtained from global average RFs.