The gas-phase and heterogeneous chemical conversion of nitrogen compounds occurring in the plume of an aircraft in the first two days after emission were investigated with a newly developed aircraft plume model. A parameterization was developed for global chemical transport models to account for the subgrid chemical processes taking place in the plume of an aircraft. The role of different plume dynamics, heterogeneous chemistry, ambient temperatures and concentrations, and different aircraft types in the chemical conversions in the plume were studied. The calculated parameters, relating the aircraft emissions to effective emissions of the aircraft plume after two days, were found to be largely dependent on season, latitude and altitude. In the North Atlantic flight corridor approximately 30% to 70%, depending on the season, of the emitted nitrogen oxides are converted to other oxides of nitrogen in the plume within the first two days.