The Lockheed A-12's were constructed mostly of titanium to withstand aerodynamic heating.
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The Lockheed A-12 family, known as the Blackbirds, were designed by Clarence “Kelly” Johnson. They were constructed mostly of titanium to withstand aerodynamic heating. Fueled by JP-7, the Blackbirds were capable of cruising at Mach 3.2 and attaining altitudes in excess of 80,000 feet. The first version, a CIA reconnaissance aircraft that first flew in April 1962 was called the A-12. An interceptor version was developed in 1963 under the designation YF-12A.
1974NASA Photo › YF-12 Project Description