Experimental aircraft speeds to more than 3,000 mph in test flight - latimes.com
At about 50,000 feet, near Point Mugu, it was released like a bomb and engaged a solid rocket booster that accelerated it to Mach 4.8 in about 26 seconds.
After separating from the booster, the X-51A scramjet engine then lit and sped to Mach 5.1 at 60,000 feet.
Talk about acceleration!
That has to be a kick in the pants (eventually
)