WASHINGTON - Supporters of the merger of Delta and Northwest airlines are working both their inside and outside games, as company executives and labor union leaders head to Capitol Hill today to testify on how the deal would affect America's aviation industry.

The congressional hearing, the third on the merger, comes as Delta has reinforced its lobbying team with some of the best-known firms on Washington's K Street.

The merger also is getting help from advocacy groups, including from an unexpected quarter.

The Consumer Federation of America, which typically lobbies hard against big business, is preparing to endorse the merger plan at Wednesday's hearing. That will be held by the Senate Commerce Committee's aviation subcommittee, which includes Sen. Amy Klobuchar, D-Minn.

Mark Cooper, the federation's director of research, said he would be testifying in favor of the proposal to create the world's largest air carrier because the current condition of aviation is so dismal.

"If you think about the prospects of opposing the merger and saying we want to keep the industry the way it is -- well, it stinks," Cooper said. "The industry pleases no one. Consumers hate it, labor hates it, investors hate it."

Cooper said the merger proposal is "an admission of a fundamental failure" of the deregulation of airlines. He argued that Congress should not try to block the deal but should pass federal laws and rules to protect passengers' rights.

Advocacy groups with close ties to the business community and conservative causes also are jumping into the debate on behalf of the airlines.

The combined new airline would have "the resources and might to weather the difficulties that have plagued other airlines," said Robert K. Johnson, president of Consumers for Competitive Choice, in a press release that called the merger "pro-consumer."

A Washington-based group, Citizen Outreach, fired off an e-mail to 25,000 supporters nationwide saying the Delta-Northwest combination would mean more stability for airlines. The head of the group, Chuck Muth, said he would monitor the merger's progress and launch a "grass-roots" effort if the deal runs into trouble as it seeks approval from the Department of Justice's antitrust division.

Citizen Outreach and Consumers for Competitive Choice both receive backing from the business community, but they denied receiving funds from Delta or Northwest.

A third group, the Center for Individual Freedom, last week circulated a statement calling the merger good for U.S. competition in the global market. A spokesman declined to reveal the source of the group's funding.

The merger continued to face opposition from labor unions, including the International Association of Machinists and Aerospace Workers, which represents many Northwest employees. A union official was scheduled to address the Senate hearing today.

Also set to appear are Doug Steenland, president and chief executive officer of Northwest, and Delta's chief executive, Richard Anderson.

In the first round of hearings last month, Anderson's contingent included, among others, Rodney Slater, the former U.S. secretary of transportation, who is now at Patton & Boggs, the top-grossing lobbying firm in the capital, according to federal disclosures.

Other big-name lobbyists recently hired by Delta include former Sen. Trent Lott, once the Republican leader in the Senate, and his partner John Breaux, a former Democratic senator.