Advanced and innovative aircraft concepts that are fuel efficient, and have a reduced environmental footprint are important in both the defense and commercial sectors. Increased interest in UAS platforms also requires significant departures from traditional aircraft designs. To enable introduction of new aircraft into the inventory, the conceptual design of advanced concepts is critical, and introducing physics based analysis early in the design space is useful. In particular, weight estimates based on statistical relations are inadequate for new concepts. Rapidly obtaining reasonably accurate airframe weight and center of gravity estimates during the conceptual design of unconventional configurations would be very useful. To address this, IAI and its collaborators from Stanford University propose Variable Complexity Weight Estimation for Conceptual Aircraft Design Optimization (VaC-CADO), a conceptual-level aircraft design tool for the design of advanced airplanes. This tool combines variable complexity optimization with appropriately sized stochastic Finite Element Modeling (FEM) methods for improved weight estimation of unconventional aircraft. This is a novel technique that leverages and enhances the state-of-the-art in aircraft design using the IAI and Stanford team's extensive experience in this field.