somewhat less maneuverable than MiG-17s. They also saw action with the North Vietnamese and became a popular export aircraft, with more than 8,000 produced. MiG-21s were designated as: YF-110B Soviet MiG-21F-13 NATO:"Fishbed-C/E" (Serials assigned: 75-001, 75-004 and 75-010) YF-110C Chinese Chengdu J-7B (MiG-21F-13 variant) YF-110D Soviet MiG-21MF NATO:"Fishbed-J" Mikoyan-Gurevich MiG-23 were the MiG-21's replacement. Their swing-wing was patterned on that of the F-111, but unlike their US antecedent, the MiG-23s were small and light enough to serve as dogfighters. MiG-23s were designated as: YF-113B Soviet MiG-23BN NATO:"Flogger-F" YF-113E Soviet MiG-23MS NATO:"Flogger-E" In addition, unconfirmed Soviet aircraft flown were MiG-25 Foxbat (YF-116); MiG-29 Fulcrum (YF-118) and Sukhoi Su-22 Fitter (YF-112). Crashes associated with the foreign aircraft included the 1979 Tonopah MiG-17 crash during training versus an F-5 and the 1984 Little Skull Mountain MiG-23 crash which killed a USAF general, Robert M. Bond. Aerial dogfights were staged between the various MiG models against virtually every fighter in US service, and against SAC's B-52 Stratofortress and B-58 Hustlers to judge the ability of the bombers countermeasures systems, they performed radar cross-section and propulsion tests that contributed greatly to improvements in US aerial performance. All the models had quirks. The MiG-17 did not have an electric seat, so pilots had to use cushions to position themselves properly inside the cockpit. Both it and the MiG-21 had pneumatic brakes applied by squeezing a lever on the front of the stick. Many of the MiG-21s did not have steerable nose gears, making them difficult to taxi; the sign of a novice Fishbed pilot was the zigzag track he made while moving on the ground. If a pilot put the throttle back on a MiG-21, it would take a long time to spool up again when trying to accelerate. Thus many of those who flew it stayed on afterburners as much as possible. The MiG-23 did not have that problem, as it was designed for speed—but it was unstable and difficult to fly. None of the Soviet-designed aircraft at Tonopah flew in bad weather or at night. All were very short-legged, compared to contemporary US aircraft, and sorties were limited to 20 minutes or so. The MiGs had US airspeed indicators and a few other minor instrument and safety modifications. Other than that, they were stock—down to their Warsaw Pact paint jobs. Two pilots of the 4477th died flying the Soviet planes. The pilots had no