WASHINGTON — While talk of a combined Delta-Northwest and other airline mergers seems to be circling the gate, further delays could jeopardize carriers' chances of getting regulatory clearance under the business-friendly Bush administration.

Antitrust experts say any such combination will take several months to gain Justice Department approval, and that a decision likely would be needed before Election Day or the airlines will have to roll the dice with whomever succeeds George W. Bush in the White House.

"The Bush administration has rarely met a merger it didn't like," said Darren Bush, an associate professor at the University of Houston Law Center who worked in the Justice Department's antitrust division from 1998 to 2001. But the airlines "have to get it done by the end of April if they have any hope of getting it (approved) under the Bush administration," he said.

The carriers are convinced the Bush administration is more supportive of their "business efficiencies argument" than the "constituency argument" that may play better with a Democrat or John McCain in the White House, said Michael Waxman, a professor at Marquette University Law School in Milwaukee.

Since talks began a few months ago, lawmakers have railed against the proposed combination of Northwest Airlines Corp. and Delta Air Lines Inc., seeing it as competition killer and fare booster. Many in Congress have promised hearings if any mergers are announced, but antitrust review responsibility ultimately falls to the Justice Department.

A spokeswoman for the Justice Department's antitrust division would not comment on how long a review could take.

Andrew Steinberg, who until mid-January was assistant secretary for aviation and international affairs at the Transportation Department, said a deal could be approved in a matter of months — if the two sides were well prepared and willing to compromise. That could leave the companies some wiggle room, but not much.

"By the summer, they're running out of time," he said.

Antitrust concerns have grounded potential deals before. In July 2001, more than a year after it was originally proposed, an attempt to merge United Airlines and US Airways fell apart amid concerns that the combined carrier would control too much of the Washington, D.C., market and dominate other key routes.

But in the case of Eagan, Minn.-based Northwest and Atlanta-based Delta, there is little overlap in most markets. And that, say observers, makes it more like the America West and US Air combo — which won Bush administration approval in June 2005, a month after it was proposed.

Fundamental changes in the airline industry may also smooth the regulatory road for Delta and Northwest. Low-cost carriers are gaining market share at the same time that record oil prices are threatening profits.

Many on Wall Street are pushing for consolidation as a way for the industry to shed additional domestic capacity and shore up its pricing power. Fewer seats in the system means higher ticket prices.

But the Delta-Northwest deal seems to be taking its cue from so many tarmac-stuck flights: going nowhere soon.

Last week, Delta's pilots union rejected arbitration with its counterpart at Northwest to break a deadlock over integration of seniority lists.

Delta has said no seniority protection means no deal.