During the Cold War a great many aircraft were built and flown but for various reasons never entered operational service. Some were losers in 'fly-off' competitions, others represented journeys up 'blind alleys' in aircraft development, and others were cancelled on dubious financial and/or political grounds. This book examines in detail the histories of these aircraft, and seeks to answer the following questions: - What might the world's air forces be like today, had the aircraft in this book entered service? - How much did German wartime design contribute to today's combat aircraft? - To what extent did so-called 'experts' influence politicians in cancelling major projects? - Was Duncan Sandys really responsible for the disastrous planning decisions taken in Great Britain in the late 1950s? - Could Great Britain have taken the lead in supersonic flight in 1946 - and kept it? - Could supersonic VTOL have become a reality in the 1960s?