AbstractThe deregulation of the US domestic airline market in 1978 and its apparent relative success continues to attract a great deal of interest among US and other economists. This uniquely US experience has clearly shown that factors such as market contestability, the multiple output nature of costs, the structure of networks and airport presence play a crucial role in the survival and, ultimately, profitability of relatively free and unregulated airlines. However, most international airlines still operate in a heavily regulated environment. While the tendency is clearly toward liberalization, the question remains: What can these airlines do to improve their profitability within this framework? Our results indicate that profitable airlines have high passenger load factors, a relatively low proportion of capacity related costs, younger and more efficient fleets and supplement their passenger loads with freight.