The D-558-1 Skystreak and its successor, the D-558-2 Skyrocket—the first manned aircraft to reach twice the speed of sound—are a proud part of a heritage of high-speed innovation at Boeing that also includes other record-breaking research aircraft, such as the triple-sonic XB-70, the hypersonic (Mach 5 and above) X-15 rocket plane and the Space Shuttle.