Calculations are presented for the NASA ER 2 aircraft at high altitude to simulate measurements taken of its own emissions during a wake-crossing event. Results are presented for a Mach=0.71 case in the lower stratosphere with an engine NOx emission index of 4.6 corresponding to the measured value. A series of codes was used in the analysis to calculate the flow field and chemical kinetics, from the engine combustor out to a distance of about 20.2 km (97 s). Initial plume properties were calculated with a two-dimensional computational fluid dynamics (CFD) code with finite rate chemistry. The results of the plume code initialized a three-dimensional parabolized Navier-Stokes (PNS) reacting flow solution, where the plume dynamics interacting with the aircraft wake were calculated out to the region of plume breakup. Results show that the early shape and mixing rate of the engine exhaust plume are dominated by the presence of the aircraft vortex wake. Model results for NOY emissions compare well to in situ measurements taken in the field. Calculated exhaust species evolutions predict several species ratios in good agreement with field data. The mixing rate of the engine plume was also predicted to be consistent with dilution measured in the field. ¿ American Geophysical Union 1996