Documentary tracing how human understanding of the jet stream - a ribbon of fast moving air high in the atmosphere - has grown. It has been responsible for bewildering effect on bomber pilots during the Second World War, turbocharging modern transatlantic flyers, the infamous 1987 hurricane and devastating floods. Scientists believe this powerful weather phenomenon is now changing its pattern of behaviour and could have an even bigger impact on our climate and the way we live our lives. Interviewees include Sir Brian Hoskins, University of Reading and Kirsty McCabe from the BBC Weather Centre.