SCRAM Jet engines offer the potential for up to Mach 15 atmospheric flight. At these speeds, one could fly from Ney York to Syndey in under 2 hours. Satellites could also be launched into orbit much more cheaply with a SCRAM jet than with rockets alone since rockets must carry their oxidiser. Unlike traditional jet engines, SCRAM jets have no moving parts and rely on air compression alone to ignite fuel at very high speeds.
While wind tunnel experiments have shown the potential of SCRAM jets for many years, expensive field tests have been rare but promising. Reuters reports that another successful field test has been carried out over the Australian outback. The experiment results from the collaboration of the Austrialian Defence Science and Technology Organisation and the American Defense Advanced Research Projects Agency (DARPA). DARPA, the original creator of the Internet, is one of the few truly profitable and effective components of the United States military.
*Update* I have been informed by an esteemed SCRAM Jet research engineer at Cal Tech that depending on fuel, the theoretical maximum speed could be as high as M 25.