Reduced gravity combustion experiments were performed aboard the International Space Station with individual methanol and n-heptane droplets that had initial diameters in the 1.2-5.0-mm-size range. Experiments were performed with air-inert mixtures at 0.1 and 0.07 MPa and about 298 K, where the monatomic gases helium and xenon were separately used as the added inert. These two gases have the same thermodynamic properties on a molar basis, but their transport properties are significantly different, allowing investigation of transport property effects, such as Lewis number variations on combustion phenomena. The results indicate that ambient gas transport properties play an important role in determining limiting oxygen indices as well as burning rates and radiant heat output histories of flames. However, comparison with drop tower data suggests that initial droplet diameters may not play a significant role in determining limiting oxygen index values.