From USNI News, the US is investigating the development of hypersonic weapons, flying at speeds of at least Mach 5 as part of it's global strike program since the 1990's. This report has been presented to Congress, in a effort for funds to continue development of this new system , and gives an interesting view on background, and issues for Congress. Go to ' document ', download document.

Report to Congress on Hypersonic Weapons - USNI News