(September 18, 2013) -- The Justice Department’s stunning decision to challenge the proposed $11 billion US Airways-American Airlines merger continues to send shock waves through the usually placid antitrust world. The lawsuit, joined by six states and the District of Columbia, was filed last month after seven months of investigation and after negotiations between the parties failed to head it off. It has divided commentators who see the case as further evidence that the antitrust division is reinvigorated and unafraid to take big, powerful players to court from others who see it as a misguided salvo that fails to understand the airline industry. One thing about which there is consensus: the stakes are sky-high for both sides....