“If United and Continental merge, another domino in a chain of mergers will fall, and there will be strong pressure for further consolidation. As I predicted when I wrote your predecessor in 2008 on the Delta-Northwest merger, approval of that merger created conditions that have persuaded Delta’s competitors to pursue their own combinations. The United-Continental transaction is the latest, but it likely will not be the last,” Oberstar’s letter reads.

Oberstar urged the Justice Department to consider three primary issues:

• Whether the transaction presents a reasonable possibility that further consolidation activity among competing carriers will follow;

• Whether, to avail itself of the potential benefits of the transaction, the combined carrier is likely to substantially eliminate capacity in such a way as to eliminate travel options between any city-pairs; and

• Whether the transaction would alter the structure of the U.S. airline industry in such a way as to permit the three largest carriers to create or enhance market power or to facilitate its exercise in either the domestic or the international marketplace.

Oberstar warned that the combination of domestic consolidation and international alliances among the major airlines will result in the world aviation market being carved up by three international mega-carriers. He asked the department to give his concerns full consideration when evaluating the merger because the transaction “could have major and lasting consequences” for American consumers.