This book combines the research activities of the authors, both of whom are researchers at Ecole Nationale de l'Aviation Civile (French National School of Civil Aviation), and presents their findings from the last 15 years. Their work uses air transport as its focal point, within the realm of mathematical optimization, looking at real life problems and theoretical models in tandem, and the challenges that accompany studying both approaches.The authors' research is linked with the attempt to reduce air space congestion in Western Europe, USA and, increasingly, Asia