CHARLOTTE ( TheStreet) -- From many quarters, pressure is mounting on the U.S. Justice Department to drop its lawsuit opposing the proposed merger of US Airways ( LCC) and American ( AAMRQ). On Wednesday, the mayors of seven hub cities -- Charlotte, Chicago, Dallas, Fort Worth, Miami, Philadelphia and Phoenix -- sent a letter to Attorney General Eric Holder, asking him "to reconsider this ill-conceived lawsuit." Most prominent among the mayors is Rahm Emanuel of Chicago, who was President Obama's chief of staff from 2008 to 2010. Also Wednesday, Oklahoma Attorney General E. Scott Pruitt served notice that Oklahoma will file a "friend of the court" brief in support of the merger. "The Department of Justice should drop its lawsuit and allow the merger of American Airlines and US Airways to continue," Pruitt said in a press release. Tulsa, Okla., is the site of American's largest maintenance base. Three weeks ago, Texas Attorney General Greg Abbott dropped his opposition to a merger, leaving six attorneys general joined with the Justice Department in support of the lawsuit and 45 attorneys general not in support of the lawsuit. Last week, 68 Democratic members of Congress sent Obama a letter advocating for the merger. "Maybe someone at Justice may not have understood the impact (of stopping the merger) would have on union workers and on thousands of jobs," said Texas Congressman Marc Veasey, in an interview. "This is management and labor working together. Justice may not have had a good understanding that (its action) would create a duopoly." Labor support for the merger has been unprecedented and may conceivably have an impact on a Democratic administration that has generally had labor support. "What is so frustrating here is that DOJ doesn't seem to consider the attitude of employees, flight attendants in particular," said Laura Glading, president of the Association of Professional Flight Attendants and perhaps the most visible labor supporter of the merger. "Shouldn't we be figured into the equation?" Glading asked in an interview. "Nobody considers the employees who made the sacrifices, did everything right, willing to change the company -- and now getting kicked in the teeth by a Democratic administration."