National Aeronautics and Space Administration has conducted tests to determine the mechanical properties of materials suitable for use in a supersonics transport over the temperature range of interest and after prolonged exposure to temperature. On the basis of studies on fatigue behavior, rate of fatigue crack propagation, residual static strength, and resistance to deterioration of properties due to prolonged exposure to temperature, no serious materials problems are anticipated. However, stress corrosion is found to be a potentially serious problem in titanium alloys in a hot salt environment and in stainless steels in an ambient environment. The-Ti-8A1-lMo-lV alloy is found to be generally superior to other contending materials in all respects studied except for salt stress corrosion in which respect it was poorer than all others. Further research is recommended on stress corrosion; on the combined effects of fatigue, thermal exposure, and creep; and on the development of structural configurations and fabrication procedures suitable for the supersonic transport.