The pioneering work on technical efficiency of Debreu and Farrell has received renewed interest with the development of Data Envelopment Analysis (DEA), a mathematical programming approach to frontier estimation pioneered in Charnes, Cooper and Rhodes (1978) and extended in Banker, Charnes and Cooper (1984). This method is seeing increasing adoption as a management tool within the general framework of performance measurement and monitoring. In recent years, applications of this methodology have been reported in a variety of production contexts. The central focus of this monograph is the application of Data Envelopment Analysis models in the productive context of air transportation.