When a U.S. Army Apache gunship that was brought down, intact, on the third day of the Iraq war, the pilot and weapons officer were captured. The fear was that the Iraqis would get their hands on its advanced radar and fire control system. These items are considered quite valuable to Russian or Chinese weapons makers. And the Russians and Chinese always pay top dollar for slightly damaged American aircraft, missiles or smart bombs. The fear was well founded. Before a bomber could destroy the helicopter, the Iraqis brought in a flatbed truck with a crane, loaded the eight ton Apache and drove off. Oops. There were visions of the helicopter being disassembled and the valuable bits smuggled out of the country. The helicopter was found, intact, outside the Baghdad airport and a 1,000 pound bomb was dropped directly on the Apache. Two weeks later, when the 3rd Mech division rolled into the airport, what was left of the Apache (not much) was found and trucked back to Kuwait. The trade in slightly damaged American equipment has been going on for some time. Because of this, when an M-1 tank was disabled during a raid into downtown Baghdad, it had to be destroyed with fire to prevent the high tech fire control and computer systems being taken. In 1999, Serbs spirited components of crashed cruise missiles and an F-117 stealth aircraft out of the country, apparently to Russia. During the Vietnam war, American warplanes downed in North Vietnam were often examined by Russian and Chinese technical experts. Captured American equipment was then sold or given to China and Russia. In the next decade, new Russian and Chinese weapons appeared that showed the influence of these items. The only way to deal with this sort of thing is to destroy downed warplanes and missiles as quickly as possible. This is relatively easy with aircraft, but it's harder to keep track of missiles. You can minimize this kind of technology transfer, but you can't always eliminate it.