High temperature stabilized SiC-based matrices will enable operation of SiCf/SiC ceramic composites (CMCs) at temperatures well above 2700?F. Use of CMC-based components such as combustor liners, turbine shrouds, and turbine vanes will enable higher temperature operation of turbine engines in subsonic, supersonic, and hypersonic aircraft. The lighter weight of the CMC components will reduce fuel consumption and their higher temperature operation will reduce air cooling requirements, decrease NOx emissions, and improve overall engine efficiency. These factors will result in significantly reduced costs for aircraft engine operation and the increase in performance afforded by CMCs will be an enabling factor for Low-Cost and Reliable Access to Space (LCRATS). Commercial aircraft engines, both large and small, will benefit from low-cost, technically superior CMCs that enable higher temperature operation of CMC-based components. In addition, CMCs are currently being tested in ground-based gas turbines for power generation, where long-life high temperature survival is of particular importance.