In this paper an airport and airline choice model, based on a nested multinomial logit model, is developed to investigate both airport competition and airline competition in a metropolitan area with multiple departure airports. The model can be used to analyze the effects of, e.g., an improvement in accessibility of a specific airport in a metropolitan area. It is shown analytically that if the frequency elasticity of demand is smaller than 1, unique airfare-frequency and passenger-charge equilibria exist. Next, symmetric equilibria are derived analytically; their properties are also examined. Finally, asymmetric equilibria are derived numerically, while their properties are discussed as well. © 2000 Academic Press.