When World War I began in 1914, the air forces of the opposing nations consisted of handfuls of rickety biplanes from which pilots occasionally took pot shots at one another with rifles. By 1918, the fighter had become an efficient killing machine with a growing strategic impact on the outcome of the war. With the help of a unique collection of meticulously recreated flying replicas, NOVA traces the story of the designers, engineers, and brave pilots caught up in the race to dominate the skies over the western front.