Could engineers in 1939 reverse-engineer a modern AIM-9 Sidewinder quickly enough to affect the Second World War?
Short answerNo; the seeker, computing, propulsion, and manufacturing prerequisites are too far beyond 1939, so meaningful effects would arrive much later.
NotesThe finished missile depends on layers of theory and industrial technique that the hypothetical recipients do not possess. Its seeker, control electronics and rocket motor could not simply be copied into wartime production. Having the hardware would therefore leave much of the necessary research and manufacturing work undone. Whether an early Sidewinder could detect enough heat from a piston-engined aircraft is raised as a question rather than settled. Even the historical postwar development required years, so the panel expects useful effects much later than the Second World War.