The impact of NOx from aircraft emissions, lightning, and surface contributions on atmospheric nitrogen oxides and ozone in the North Atlantic flight corridor has been investigated with the three-dimensional global chemistry transport model TM3 by partitioning the nitrogen oxides and ozone according to source category. The results have been compared with Pollution from Aircraft Emissions in the North Atlantic flight corridor (POLINAT 2) and Subsonic Assessment Ozone and Nitrogen Oxide Experiment (SONEX) airborne measurements in the North Atlantic flight corridor in 1997. Various cases have been investigated: measurements during a stagnant anticyclone and an almost cutoff low, both with expected high aircraft contributions, a southward bound flight with an expected strong flight corridor gradient and lightning contributions in the south, and a transatlantic flight with expected boundary layer pollution near the U.S. coast. The agreement between modeled results and measurements is reasonably good for NO and ozone. Also, the calculated impact of the three defined sources was consistent with the estimated exposure of the sampled air to these sources, obtained by specialized back trajectory model products. Model calculations indicate that aircraft contributes 55% to the mean NOx concentration and 10% to the O3 concentration in the North Atlantic flight corridor in October 1997, whereas lightning and surface emissions add 15% and 25% to the NOx concentration and 20% and 30% to the O3 concentration. ¿ 2000 American Geophysical Union