The Skunk Works had predicted that the U-2 would have a limited operational life over the Soviet Union. The CIA agreed. In late 1959, Skunk Works received a contract to build five A-12 aircraft at a cost of $96 million. Building a Mach 3.0+ aircraft out of titanium posed enormous difficulties, and the first flight did not occur until 1962. (Titanium supply was largely dominated by the Soviet Union, so the CIA set up a dummy corporation to acquire source material.) Several years later, the U.S. Air Force became interested in the design, and it ordered the SR-71 Blackbird, a two-seater version of the A-12. This aircraft first flew in 1966 and remained in service until 1998.