Long before the CIA's Gary Power's U2 was shot down in 1960, the RAF had been flying secret spy flights over the Soviet Union. These "peacetime" missions were dangerous, provocative and part of a 20-year undeclared espionage war waged high over the Soviet Union. Over 40 allied aircraft were shot down and over 250 aircrew lost. British, American and Soviet air force pilots involved tell their story, while relatives of missing air crew are now trying to find out what happened to their loved ones.