Trace gas measurements of NO, NOy, CO and O3 performed on board the DLR aircraft Falcon are used to examine the interhemispheric differences for midlatitudes during local autumn. The measurements were part of the INCA campaign (Interhemispheric differences in cirrus properties due to anthropogenic emissions). Major deployment sites were Punta Arenas, Chile (53°S) and Prestwick, Scotland (55°N). In addition, the meridional distribution of trace gases measured during the transfer flights between Germany and Chile were analysed for latitudes between 60°N and 60°S. Median mixing ratios of NO, NOy, CO and O3 in the upper troposphere in the investigation area near Prestwick exceed the observed concentrations in Punta Arenas by factors of 4.5, 3, 1.5 and 1.2, respectively, due to the influence of convective vertical transport of polluted boundary layer air and aircraft emissions. The INCA measurements at northern midlatitudes agree well with the data of previous campaigns such as NOXAR and POLINAT 2. Based on selected case studies net ozone production was calculated from O3, NO, CO and H2O measurements. For these estimates the chemical reactions with hydrocarbons were neglected and model results were used for the ozone photolysis frequency and the OH concentrations. The results for Punta Arenas show net ozone production for the upper troposphere, but net ozone destruction for the middle troposphere due to the very low NO levels observed there. For northern midlatitudes a significant net ozone production was calculated for the middle and upper troposphere caused by the higher concentration levels of ozone precursors in the region of the North Atlantic flight corridor. The meridional trace gas distributions in the upper troposphere show strongly enhanced CO and NOy concentrations over tropical South America. These air masses encountered deep convection over the Amazon basin and are distributed over a large area due to an upper level anticyclonic flow over South America, which is typical for the wet season. Long-distance transport of CO emissions from West African biomass burning sites partly contributes to the high CO concentrations over the tropics. Comparisons of the INCA measurements for the Southern midlatitudes with the chemical transport model MOZART show that CO and NOy concentrations over Punta Arenas are overestimated by the model. Probably the assumptions for the local surface emissions and the long-distance transport of biomass burning emissions are too high. In addition the tropopause height simulated by the model is too low. Except for the tropopause region the model simulates ozone and nitrogen oxides in good agreement with the observations. The net chemical ozone production calculated by the model agrees well with the estimates based on the measurements. For comparison with the INCA data for the northern midlatitudes model simulations of MOZART and NILU were used. The measured CO profile over Prestwick was well represented by the regional NILU simulation. In contrast, the MOZART model sometimes showed more than twice the amount of CO observed. This can be caused by the rough resolution of the model and the assumption of too high surface emissions in Europe. The observed trace gas distributions of NO, NOy and O3 are well reproduced by the model. For the upper troposphere the net ozone productions calculated by the models agree well with the results of this study calculated directly from the observations. Only in the middle troposphere lower net ozone production rates than simulated by the CTM were calculated from the observations due to the neglection of the hydrocarbon chemistry.