occurred, the internal Lockheed designation changed from Archangel-1 to Archangel-2, and so on. These names for the evolving designs soon simply became known as "A-1", "A-2", etc. The CIA program to develop the follow-on aircraft to the U-2 was code-named Oxcart. These designs had reached the A-11 stage when the program was reviewed. The A-11 was competing against a Convair proposal called Kingfish, of roughly similar performance. However, the Kingfish included a number of features that greatly reduced its RCS, which was seen as favorable to the board. Lockheed responded with a simple update of the A-11, adding twin canted fins instead of a single right-angle one, and adding a number of areas of non-metallic materials. This became the A-12 design. On 26 January 1960, the CIA ordered 12 A-12 aircraft. New materials and production techniques Because the A-12 was well ahead of its time, many new technologies had to be invented specifically for the Oxcart project with some remaining in use in present day. One of the biggest problems that engineers faced at that time was working with titanium. In his book Skunk Works: A Personal Memoir of My Years at Lockheed, Ben Rich stated, "Our supplier, Titanium Metals Corporation, had only limited reserves of the precious alloy, so the CIA conducted a worldwide search and using third parties and dummy companies, managed to unobtrusively purchase the base metal from one of the world's leading exporters – the Soviet Union. The Russians never had an inkling of how they were actually contributing to the creation of the airplane being rushed into construction to spy on their homeland." Before the A-12, titanium was used only in high-temperature exhaust fairings and other small parts directly related to supporting, cooling, or shaping high-temperature areas on aircraft like those subject to the greatest kinetic heating from the airstream, such as wing leading edges. The A-12, however, was constructed mainly of titanium. Titanium is quite rigid and difficult to machine, which made it difficult to form into curves given available techniques. This made it difficult to form the leading edges of the wing and similar surfaces. The solution was found by machining only small "fillets" of the material with the required shape and then gluing them onto the underlying framework which was more linear. A good example is on the wing: the underlying framework of spars and stringers formed a grid, leaving triangular notches