The book provides deep insights into the operations and business of the air transport system, i.e., airlines, airports, and ATC/ATM (Air Traffic Control/Management). It reviews activities of the air transport operators, functions and processes, as well as the needs and requirements of users and customers in a simple and easy to understand way. A brief description of aviation history, the air transport system development and processes are followed by the elaboration of the aircraft's elements, masses, payload-range diagrams, and balance. The fundamentals of airports and the ATC/ATM service providers and their contribution to the air transport system are also provided. Moreover, the most important elements in the airport and ATC/ATM system are examined, and the rules, regulations and simplified approaches to how these systems operate are described. The airlines play an important role in the air transport system as users of the airports' and ATC/ATM service providers. Different business models are presented as well as the fundamentals of airline planning, operations and management (including passenger demand, market segmentation, scheduling, tariffs, alliances, and frequent flyer programs). Besides passenger transport, the book contains an overview and comprehensive guide of the air cargo transport by addressing the key issues such as: the current trends, market characteristics, unit load devices, cargo handling, air cargo documents, and transport of different kind of goods (perishable, live human organs, live animals, dangerous, heavy, etc.).