This chapter reviews the effects of air transport liberalization, and investigates the roles played by airport-airline vertical arrangements in liberalizing markets. Our investigation concludes that liberalization has led to substantial economic and traffic growth. Such positive outcomes are mainly due to increased competition and efficiency gains in the airline industry, and positive externalities to the overall economy. Liberalization allows airlines to optimize their networks, and thus may introduce substantial demand and financial uncertainty to airports. Vertical arrangements between airlines and airports may offer a wide range of benefits to the parties involved, yet such arrangements could also lead to airline entry barriers which reduce the effects of liberalization. Three approaches have been developed to model the effects of liberalization in complex market conditions, which include the analytical, econometric and computational network methods. These approaches should be selectively utilized in policy studies on liberalization.