The use of advanced composite structures in aircraft gas turbine engines is increasing as weight and cost reductions become more difficult to achieve with conventional and even quite sophisticated metal designs. The present outer duct of the F404 engine is a chemically-milled titanium part. It is the objective of the program described in this paper to reduce the weight and cost of this component through the use of advanced composite materials. Starting in 1979, under Navy and NASA sponsorship, a graphite/PMRl5 version of the F404 outer duct has been going through its design and development phases. Two complete ducts were built under this portion of the program. One duct has accumulated over 1200 hours of ground engine testing while the other duct has been successfully static tested. Based on the design, fabrication, and test effort accomplished to date, a significant cost savings and a 10% weight reduction are projected for the composite duct versus the current titanium duct.