A three dimensional regional chemistry transport model driven by data from a weather prediction model was applied to deliver chemistry forecasts suitable for scientific flight planning purposes throughout the POLINAT 2 measurement campaign from September to October 1997. The forecasts gave an overview of the expected distributions of ozone and its precursors in possible flight regions, including a separation of the influence of the aircraft NOx source on upper tropospheric NOx and ozone concentration, from lightning, surface and stratospheric sources. The usefulness was documented several times during the campaign, in particular for the investigation of corridor effects due to North Atlantic air traffic emissions. ¿ 2000 American Geophysical Union