Multiplex Airline Networks: an Application to the Italian Air Transport System

In recent years, the European air transport sector has undergone profound changes, largely driven by market liberalization. This process has enabled airlines to develop autonomous strategies, fostering the emergence of a more heterogeneous and competitive environment. Today, the network models adopted by different carriers play a central role in understanding how passenger flows are structured, how connections are distributed and what the implications are in terms of costs, accessibility and sustainability. Within this context, two main organizational models can be identified: the Hub-and-Spoke, typical of traditional full-service carriers, and the Point-to-Point, prevalent among low-cost carriers. The former concentrates traffic through a limited number of major hubs, offering wide connection opportunities but at higher costs; the latter favors direct connections, resulting in a more distributed and flexible network that aims at cost reduction and operational efficiency. This thesis examines these dynamics in the Italian context by applying tools from network science, with a particular focus on multilayer models. In this approach, each airline is represented as a distinct “layer” of the network, superimposed on the others, with airports as nodes and routes as links. Such representation makes it possible to analyze not only the structure of individual networks but also the interactions and overlaps between different strategies. From a predictive point of view, models were implemented to estimate the probability of connections between airports. The main contribution of this work lies in demonstrating the usefulness of a multilayer approach to analyze and compare airline strategies. In conclusion, the study highlights how the structure of air transport networks is not merely an operational matter but a crucial strategic element that reflects market dynamics, shapes passenger experience, and contributes to defining the economic and environmental impact of aviation.