This video shows a X-51A Waverider scramjet completing its longest ever test flight, reaching speeds of Mach 5.1 on May 1st, 2013. The scramjet also broke the over-all record for longest air-breathing hypersonic flight.
The beginning of the video shows a ?B-52H Stratofortress which at 36 seconds releases a grey X-51A Waverider scramjet that is mounted on a white solid rocket booster. The rocket booster fires for 26 seconds to get the scramjet up to speed (Mach 5.1) then separates, allowing the scamjet to continue under its own power.
This video comes via space.com