Astronomy Picture of the Day tells about the X-43A.
Using oxygen from the air itself, a NASA experimental jet propelled itself past Mach 7 in the atmosphere above the Pacific Ocean this weekend. The small automated X-43A Hyper-X craft was dropped from a huge converted B-52 bomber and then accelerated by a standard Pegasus rocket. At Mach 7, seven times the speed of sound, the X-43A separated and the novel scramjet kicked in. Atmospheric oxygen was then scooped up, combined with onboard hydrogen, and combusted in flight to propel the X-43A to record air speeds during maneuvers over the next 10 seconds.
Even at 5,000 miles an hour you can’t get very far in 10 seconds (14 miles).