The MiG-21 posed a major threat to Israeli Air Defenses as well as to American pilots over the skies of North Vietnam. Over the next year, the IDF put in over 100 hours of testing of the MiG-21 and shared the results with the United States. In a secret agreement negotiated with the United States Defense Intelligence Agency (DIA), Israel agreed to loan the MiG to the United States in exchange for Israel purchasing the F-4 Phantom II, at the time the top-of-the-line fighter for both the USAF and United States Navy. In late 1967, a USAF DouglasC-124 landed in Israel, and the MiG was loaded into the cargo hold, and flown to Groom Lake. At Groom Lake, it was then re-assembled for flight, and evaluated in a series of test flights known as HAVE DOUGHNUT. The aircraft made its first flight at Groom Lake in January 1968. AFSC recruited its evaluation pilots from the Air Force Flight Test Center, while Tactical Air Command's were primarily United States Air Force Weapons School graduates. By mid-1968, the MiG-21 was far less of an enigma than it had been. Over 102 sorties were flown in the aircraft. On 12 August 1968, the IDF obtained two Syrian Air Force MiG-17F ("Fresco C") fighters that had gotten lost during a training flight and landed inadvertently at Betzet Landing Field, Israel. The MiG-17 was of paramount importance to the United States, because it was also used by the North Vietnamese Air Force. It was much more agile than the supersonic MiG-21, and in experienced hands it would run rings around the F-4 Phantom. After a brief period of testing, the first MiG-17, coded HAVE DRILL arrived at Groom Lake in January 1969. The second MiG-17, HAVE FERRY, arrived in March. By June 1969, the results of the evaluations of the MiG-21 and MiG-17s were incorporated into the USAF Fighter Weapons School and the Navy TOPGUN training school. In 1969 Pakistan supplied the U.S. with a Chinese built MiG-19 (J6) which was tested under the Have Drill program. These aircraft were given USAF designations and fake serial numbers so that they may be identified in DOD standard flight logs. In May 1973, Project "HAVE IDEA" was formed which took over from the older HAVE DOUGHNUT, HAVE FERRY and HAVE DRILL projects.