Online Supplement: Market Structure and Competition in Airline Markets

This section closely follows Ciliberto and Tamer (2009) (henceforth CT), and we refer to that paper for further reading. We provide a set of sufficient conditions that guarantee point identification of the model parameters in equation (1) in the main text. These conditions are natural in this context and rely on large support regressors. Our inference methods do not require that these conditions be satisfied as the moment inequalities adapt to partial identification, but we give them here to give intuition as to what exogenous variation might be helpful for gaining identification.