An experimental scramjet being developed by Australian and American scientists was successfully tested at Mach 10 over the Australian outback. That's 6,835 mph, or 10 times time speed of sound.
Scientists used a regular rocket to launch the scramjet, because scramjets need supersonic airflow and thin atmosphere to operate effectively. (Scramjet = supersonic combustion ramjet.)
Researchers hope that the general technology they're testing today leads to high speed, long range flights and low-cost satellite launches.