This study investigates the degree of complexity required in the simulation of turbulence and thunderstorm downbursts for flight simulation. A turbulence model that contains all of the correlations found in homogeneous isotropic turbulence is presented. Several simplifications and alternate models are considered. This paper also presents further developments in the simulation of thunderstorm downbursts. A single ring vortex system, a triple ring vortex system, and Joint Airport Weather Studies (JAWS) data are implemented on the University of Toronto Institute for Aerospace Studies B-747 Flight Simulator. By means of pilot evaluations on this simulator, it was found that the inclusion of the isotropic turbulence correlations did not seem to affect the pilot and not much difference was perceived among the turbulence models. Pilot evaluations of the downburst models showed that both single and triple ring vortex systems produced similar pilot reactions to actual downbursts (JAWS data). It is suggested that the ring vortex models be expanded upon to include more than one downburst cell.