We examine the relationship between the total size of an airline and its flight delays. Total size is measured by its total market share, total amount of assets, or total number of full-time equivalent employees. In our estimations, important controls are the degree of competition on the route and airport. We also add numerous other controls and route-specific fixed effects. We find that the larger an airline is nationwide, the smaller its average delay time and delay or cancellation occurrence. An origin airport with less competition may lead to more delays. A less competitive route may reduce delays.