U.S. Senator Amy Klobuchar, who has been cultivating an image as a consumer advocate, said Tuesday that the Obama administration's decision to challenge the proposed US Airways and American Airlines merger in court reflects "concerns" raised in Congress about diminished competition in second-tier markets. The Minnesota Democrat, who chairs the Judiciary Antitrust Subcommittee, held a hearing examining the proposed merger's impact on consumers and competition earlier this year. "Whether it's a family looking for affordable flights or a small business-owner looking for the best frequent flier program, we need to make sure consumers have as many choices as possible at the lowest prices and that no airline or small group of airlines has a stranglehold on the market," Klobuchar said. "At the hearing there were serious issues raised about the effect of the merger on prices in particular markets, and the Justice Department's complaint reflects those concerns."