The spatial variability and temporal behavior of the vertical flux of ozone has been investigated from turbulence measurements collected on aircraft flight legs in the daytime period during two consecutive summer experimental field studies. The data were obtained during horizontal flight legs conducted over agricultural crops and forested land in southeastern Pennsylvania, central Ohio, and western Tennessee/Kentucky. Results from individual experimental cases and statistics derived from all cases in each region are presented. Ozone flux generally exhibited a significant height dependency; strongest negative (downward) fluxes in the lowest level flight legs were primarily attributed to the uptake of ozone by the surface and vegetative cover while values were near-zero in the middle of the convective boundary layer in the afternoon period. As ozone flux was proportional to concentration, slightly higher fluxes were found in low level downwind urban plume segments where ozone concentrations were 10-20 ppb higher than in the surrounding area. Derived deposition velocity showed no such bias as a function of position across the urban plume. Ozone flux differences were not apparent between the more heavily forested sections and the primarily agricultural cropland areas in these regions. (Copyright (c) 1990 Kluwer Academic Publishers. Printed in the Netherlands.)