Performance tests
Many potential enemies of the USSR and its client states had a chance to evaluate the MiG-23's performance. In the 1970s, after a political realignment by the Egyptian government, Egypt gave their MiG-23MS to the United States and the People's Republic of China in exchange for military hardware. These MiG-23MS helped the Chinese to develop their Shenyang J-8II aircraft by borrowing some MiG-23 features, such as its ventral fin and air intakes, and incorporating them into the J-8II. In the US, these MiG-23MS and other variants acquired later from Germany were used as part of the evaluation program of Soviet military hardware. The Dutch pilot Leon Van Maurer, who had more than 1200 hours flying F-16s, flew against MiG-23ML Flogger-Gs from air bases in Germany and the U.S. as part of NATO's aerial mock combat training with Soviet equipment. He concluded that the MiG-23ML has superiority on the vertical plane over early F-16 variants, is just slightly inferior to the F-16A on the horizontal plane, and has superior BVR capability.
The Israelis tested a MiG-23MLD that defected from Syria and found that it had better acceleration than the F-16 and F/A-18.
Another MiG-23 evaluation finding in the US and Israel reports was that the MiG-23 has a Heads-Up Display (HUD) that doubles as a radarscope, allowing the pilot to keep his eyes focused at infinity and work with his radar. It also allowed the Soviets to dispense with the radarscope on the MiG-23. This feature was carried over into the MiG-29, though in that aircraft a cathode ray tube (CRT) was carried on the upper right corner that can act as a radarscope as well. Western opinions about this "head-up radarscope" are mixed. The Israelis were impressed, but an American F-16 pilot criticizes it as "sticking a transparent map in front of the HUD" and not providing a three-dimensional presentation that will accurately cue a pilot's eyes to look for a fighter as it appears in a particular direction.
Besides the Syrian defection, a Cuban pilot flew a MiG-23BN to the US in 1991 and a Libyan MiG-23 pilot also defected to Greece in 1981. In both cases, the aircraft were later returned to their countries.