We apply a detailed aerosol microphysics model to study the evolution of aerosols in the far wake of an aircraft plume. Constrained by in-situ measurements, our simulations reveal that the largest volatile particles-those most likely to contribute to the background abundance of condensation nuclei-are dominated by ion-mode aerosols formed on chemi-ions. By tracking the evolution of the aircraft-generated particles from the near wake to the far wake, we estimate the properties of the aircraft particles that are effectively injected into the upper troposphere. The entrainment of ambient vapors and aerosols into the aging plume is taken into account, which significantly affects the outcome. The model calculations reveal that a substantial number of the larger ion-mode volatile particles may survive long enough to act as potential cloud nuclei, thus perturbing the background CCN population. This perturbation is significant during the winter season, and in other locales with low background aerosol concentrations, but is likely to be negligible during the summer season or at locations with heavy aerosol loading. The implications and uncertainties of the results are discussed. ¿ 1999 American Geophysical Union