<p>We theoretically derive an optimal price for a bundle of two goods that are sold in advance to risk-averse buyers. The theory predicts that a round-trip ticket is less expensive than two one-way tickets when demands for the outbound and the inbound are uncertain and positively correlated. Using a unique airlines dataset, we find evidence that is consistent with the theory; round-trip bundle discounts exist and they are larger for passengers who buy early in advance, stay on a Saturday night, and have higher valuations. We also find that the bundle discounts decrease with competition.</p>