International Airfares in the Age of Alliances : The Effect of Codesharing and Antitrust Immunity

This paper provides empirical evidence showing the effect of airline cooperation on the level of interline fares paid by international passengers. The analysis focuses on two measures of cooperation, codesharing and antitrust immunity, and the results show their partial effects are both negative. The presence of codesharing on an international interline itinerary reduces the fare by 8-17 percent, with the exact number depending on the sample used and the estimation method. Moreover, the presence of antitrust immunity reduces the fare by 13-21 percent. Codesharing and immunity are substitutes, however, in the sense that their combined effect is smaller than the sum of their partial effects. Recognizing this difference, which is captured by an interaction variable in the regressions, the combined effect ranges between 17 and 30 percent. These results provide strong evidence that airline cooperation in the fare-setting process generates substantial benefits for interline passengers