Brothers Colin and Ewan McGregor follow up their documentary The Battle of Britain with a film exploring Bomber Command, a rarely-told story from the Second World War. The film focuses primarily on the men who fought and died in the skies above occupied Europe, with numerous examples of individual heroism and extraordinary collective spirit, and Colin learns to fly the key aircraft of the campaign: the Lancaster bomber. But this is also the story of a controversy that has lasted almost 70 years. The programme covers six years of wartime operations, and traces the obstacles and challenges that were overcome as the RAF developed and deployed the awesome fighting force that was Bomber Command.