Air Transport is a complex system. Although the idea of complexity has been introduced only recently in the scientific world, all professionals and researchers involved in the study and management of the Air Transport System would agree on this point. It is composed of a plethora of different agents, constantly interacting, sharing partial and noisy information, and pursuing different objectives. The result of these interactions – emergent behaviour – is usu-ally unwanted disturbance that affects the quality of service perceived by the customers, such as delays and cancellations, or adverse safety events. In this contribution, we will present in detail why Air Transport is considered a complex sys-tem, and how Complexity Science can contri...