A series of aircraft measurements taken in the marine boundary layer in the vicinity of Christmas Island during the NASA Pacific Exploratory Mission-Tropics (PEM-Tropics) A mission allow for a partial characterization of the turbulent transfer through the mixed layer. The measurements were obtained during a series of 12 circular sampling legs (of 30 min each) at five altitudes in the boundary layer, including the entrainment layer. The data include high-frequency measurements of moisture and the wind field in three dimensions (18.7 Hz) and slower-response temperature (1 Hz). Computed fluxes and variances are filtered using standard Fourier filters as well as moving-average filters. The uncertainties associated with the choice of filter are discussed. The vertical structure of the boundary layer and the profiles of the variance of vertical velocity are consistent with the standard conceptual picture of the mixed layer. The humidity flux and variance of vertical velocity vary by 50% between three 30-min horizontal samples midway through the mixed layer but remain essentially constant at the bottom of the mixed layer. The variability in the humidity flux and the variance of vertical velocity appear to be caused by changes in the dynamical scales associated with the transport, with a high correlation between the peak length scale derived from the cospectrum and the net flux of humidity. The observed changes in the fluxes are consistent with changes in the rate of entrainment into the mixed layer, coinciding with changes in the fraction of vertical transport associated with mesoscale processes. The vertical flux divergence of humidity appears to be significantly affected by mesoscale influences.