The political fight between American Airlines and low-cost carrier Southwest Airlines intensified on Thursday with a new drive to repeal a federal ban on direct flights between Dallas Love Field and most destinations outside Texas.

A month-long moratorium on efforts to sway federal lawmakers while local authorities and carriers tried to broker a compromise on air service passed without a deal on Thursday, and again placed the spotlight on Washington where an attempt to repeal the so-called Wright amendment fizzled last year.

Republican Representatives Jeb Hensarling and Sam Johnson of Texas said at a news conference in Dallas that they would resume their efforts to repeal the 27-year-old law when Congress reconvenes from its Memorial Day recess next week.

"Though a solution may still be found at the local level, the reality is Congress created the Wright amendment and only Congress can repeal it," Hensarling said.

In 1979, House Majority Leader Jim Wright pushed through the law restricting direct service from Love Field to other cities in Texas and several nearby states. The limit was intended to boost prospects for then-fledgling Dallas-Fort Worth Airport, which has since become American's main hub.

Over the years, Southwest has gone from a strong regional airline to a national low-cost force that challenged industry norms. It stands as the prototype of success that many airlines, especially start-ups and those trying to shed financial problems, are trying to mimic.

In recent years, Southwest has expanded in Chicago, Denver, Philadelphia and other markets and now wants the freedom to fly anywhere it wants from its Love Field home.

"The next step is to keep building legislative support. It was done in Washington and can only be changed in Washington. It's a slow but sure process," said Ed Stewart, a Southwest spokesman.

American says it would likely shift some service to Love Field to compete with Southwest in big markets if flight restrictions are lifted there.

Mary Frances Fagan, a spokeswoman for American, says there are members of Congress and "a lot of other people" who recognize that that DFW service would be "degraded" if the Love Field restriction were repealed.

More than two-thirds of American's business at DFW is connecting traffic, with many flights serving small markets.