WASHINGTON — As summer winds down, Congress is lining up its autumn hearings. But airline mergers, the subject of four hearings this spring, are not among the hot-button issues scheduled for attention.

With no more congressional reviews planned, conventional wisdom now holds that the proposed merger of Delta Air Lines and Northwest Airlines will be completed this year without any major new political objections.

Further hearings are unnecessary because "we believe that Congress saw that antitrust (violations) would not be a significant concern with this deal," Delta spokeswoman Chris Kelly said.

Politics is not supposed to play a role as attorneys at the Justice Department review a merger for possible antitrust violations. That department alone has the power to block a deal if it threatens competition in an industry.

But elected lawmakers can play an indirect role in the review process by whipping up popular sentiment to pressure the Justice Department. The House and Senate hearings held in April and May, shortly after the deal was announced, failed to create a firestorm of protests, leaving the Delta-Northwest merger seemingly cleared for takeoff in coming months.

"We are pleased with the progress that has been made and believe we are on track for completion by the end of the year," Kelly said.

Andrew B. Steinberg, an aviation attorney and former chief counsel for the Federal Aviation Administration, agreed. "I have not heard there are any problems," he said.

Justice spokeswoman Gina Talamona would say only that the review is "ongoing."

But even though the merger appears on track, some opponents say they will continue to object. Joseph Tiberi, spokesman for the International Association of Machinists and Aerospace Workers, said he is in no mood for surrender.

"We've been opposed to this from Day One, and our opposition will continue," said Tiberi, whose union represents Northwest's customer-service and reservation agents, clerical workers and equipment service employees. "We will continue meeting with members of Congress and take all steps possible to protect workers, because Delta and Northwest management clearly are not."

He said this year's hearings did nothing to persuade the IAM that the merger would be good for workers. "If anything, we are less comfortable with it," he said, because during their testimony, the airlines' executives pulled back from their initial pledge not to fire front-line workers.

Instead of reaffirming a no-furlough commitment, they told Congress "high fuel prices may make that impossible," he said. "We have seen Delta and Northwest change their stories."