Experiments were conducted in a closed, spherical reactor aboard NASA's KC-135 reduced-gravity aircraft using an equimolar n-C4H10+O-2 premixture (Le = 1.3) at subatmospheric pressures to compliment model predictions and further explore the reactive-diffusive structure of cool flames and ignitions. The pressure and radial temperature histories were recorded and analyzed for different initial conditions. In addition, the visible light emission from excited formaldehyde was recorded using an intensified video camera and was observed to be radially symmetric in all cases. Unexpectedly, however, the measured temperature distributions during (and after the passage of) the cool flames and ignitions were not parabolic as predicted by conduction models, which suggests the onset of weak convection at 10(-2)g.