In 2004, NASA reached a speed of Mach 9.6, or nearly 7,000 miles per hour (11,265 kph), with a jet-powered aircraft. But that vehicle, known as X-43, only flew for a few seconds and its copper-based engine was not designed to survive the flight.
Engineers have hoped to see the hypersonic X-51A travel for five minutes of powered flight. For protection from extreme heat, it uses insulation tiles, similar to those on the NASA space shuttle orbiters, according to a 2011 military description of the project.
Hypersonic flight is normally defined as beginning at Mach 5, which is five times the speed of sound.