along the leading edge that were filled with fillets. With the move to the A-12, another improvement in RCS was made by replacing the fillets with new radar-absorbing composite materials made from iron ferrite and silicon laminate, both combined with asbestos to absorb radar returns and make the aircraft more stealthy. Flight testing After development and production at the Skunk Works, in Burbank, California, the first A-12 was transferred to Groom Lake test facility (Area 51). On 25 April 1962 it was taken on its first (unofficial and unannounced) flight with Lockheed test pilot Louis Schalk at the controls. The first official flight took place on 30 April and subsequent supersonic flight on 4 May 1962, reaching speeds of Mach 1.1 at . The first five A-12s, in 1962, were initially flown with Pratt & Whitney J75 engines capable of thrust each, enabling the J75-equipped A-12s to obtain speeds of approximately Mach 2.0. On 5 October 1962, with the newly developed J58 engines, an A-12 flew with one J75 engine, and one J58 engine. By early 1963, the A-12 was flying with J58 engines, and during 1963 these J58-equipped A-12s obtained speeds of Mach 3.2. Also, in 1963, the program experienced its first loss when, on 24 May, "Article 123" piloted by Kenneth S. Collins crashed near Wendover, Utah. Collins safely ejected and was wearing a standard flight suit, avoiding unwanted questions from the truck driver who picked him up. He called Area 51 from a highway patrol office. The reaction to the crash illustrated the secrecy and importance of the project. The CIA called the aircraft a Republic F-105 Thunderchief in news articles and official records. Two nearby farmers were told that the aircraft was carrying atomic weapons to dissuade them from approaching the crash site; and local law enforcement and a passing family were strongly warned to keep quiet about the crash. Each was also paid $25,000 in cash to do so; the project often used such cash payments to avoid outside inquiries into its operations. The project received ample funding: contracted security guards were paid $1,000 monthly with free housing on base, and chefs from Las Vegas were available 24 hours a day for steak, Maine lobster, or other requests. In June 1964, the last A-12 was delivered to Groom Lake, from where the fleet made a total of 2,850 test flights. A total of 18 aircraft