A coupled microphysical-chemical-dynamical trajectory box model simulating the emission, formation, and evolution of particles in dispersing aircraft wakes and contrails is presented. The mutual interaction pathways between the various liquid and solid aerosols are elucidated, including a discussion of the involved microphysical processes. Free model parameters are constrained using data from in situ observations. Volatile aerosol formation by binary nucleation, nonequilibrium heteromolecular condensation, sulfur-induced soot activation, and ice nucleation in wakes behind subsonic and supersonic aircraft are illustrated in case studies. ¿ 1998 American Geophysical Union