The mayors of Charlotte, N.C.; Philadelphia; Dallas; Fort Worth; Phoenix; Chicago and Miami-Dade County signed a letter Wednesday urging federal officials to end a lawsuit aimed at killing the merger.
The Justice Department lawsuit, which is scheduled to be heard Nov. 25 in Washington, claims the merger will hurt competition and lead to higher fares and reduced service to smaller markets.
The merger would create the nation's largest airline and put about 70% of U.S. domestic airline traffic in the hands of four major carriers.
"We support the merger of American and US Airways because it is based on growth which benefits consumers and our communities," the letter by the mayors stated. "A hub airport is only as good as the route network it supports, and our cities represent hubs throughout the United States that would benefit from a broader route network."
The lawsuit was originally supported by seven states and the District of Columbia, but Texas Atty. Gen. Greg Abbott announced last month that he was pulling out of the suit after American Airlines agreed to maintain scheduled daily service to more than 20 Texas airports.
Since American's parent company, AMR Corp., filed for bankruptcy in 2011, the airline has been reporting strong earnings.
Earlier this month, AMR reported its most profitable quarter in company history, with $6.8 billion in revenue and $289 million in profits for the July-through-September period.