The National Aeronautics and Space Administration sponsored a joint High-Speed Research Programme with United States airframe and propulsion companies to provide the critical high-risk technologies for a Mach 2·4, 300 passenger civil transport. Laboratory and medium-scale tests provided promising results in meeting both the environmental and economic goals for a future High-Speed Civil Transport. However, before the technologies were integrated at large and full scale, the programme was cancelled because of global economic concerns of the US transport industry.