NYTimes Report:
The Justice Department, along with the attorneys general of six states, filed a lawsuit on Tuesday seeking to block the proposed merger of American Airlines and US 
Airways.
The $11 billion deal, announced in February, took American out of bankruptcy. It would create the nation’s biggest airline, a company with the size and breadth to compete against United Airlines and Delta Air Lines, which have grown through mergers of their own in recent years and are currently the biggest domestic carriers.
But in the complaint filed Tuesday in Federal District Court in the District of Columbia, the Justice Department said that the merger “will leave three very similar legacy airlines — Delta, United and the new American — that past experience shows increasingly prefer tacit coordination over full-throated competition.”