Management of uncertainty is critical to support effective decision making throughout the design process. Unfortunately, in modern complex systems, uncertainty quantification can become cumbersome and computationally intractable for one individual or group to manage. This is particularly true for systems comprised of a large number of components. In many cases, these components are designed by different groups with analyses conducted on different computational platforms. This talk presents an approach for decomposing the uncertainty quantification task among the various components comprising a system, then synthesize these results to quantify uncertainty at the system level. We introduce concepts that extend our approach to systems containing a large number of component-to-component interface variables. We apply the proposed method to quantify how uncertainty in aviation technology affects uncertainty in environmental impacts.