ATLANTA, Georgia (AP) -- A $20 billion deal to combine Delta Air Lines and Northwest Airlines was in ""serious jeopardy"" late Tuesday because the pilots unions from both companies were unable to reach an agreement on blending their seniority lists, two people close to talks told The Associated Press.

The people said the pilots unions have agreed on a comprehensive joint contract, but they are unable to agree to how seniority for the 12,000 pilots would work under a combined carrier. The people asked not to be named because of the sensitive stage of the talks. They said that the pilot talks were expected to continue Wednesday, but if no agreement is reached, the combination of the two airlines would be in ""serious jeopardy.""
The boards of both companies were expected to vote on a combination agreement Wednesday if a pilot deal is in place by then. Otherwise, they were expected to just get an update on the merger talks, three people close to the talks said.
One of the officials close to the talks said Northwest's board might only meet by teleconference or, if things fall apart, not meet at all.
A fourth person familiar with the talks said earlier Tuesday that Delta was mulling a Thursday announcement if everything fell into place by then.
Developments
A Delta spokeswoman earlier Tuesday declined to comment on the developments. Delta has previously said it was considering a consolidation transaction, but it has not commented beyond that.
Talk of airline consolidation has heightened in recent months amid persistently high fuel prices, which are eating away at the industry's bottom line.
A combination of Atlanta-based Delta and Eagan, Minn.-based Northwest would create the world's largest airline in terms of traffic. That's before any divestitures regulators might require them to make if they combine.
There has also been speculation about a possible combination of Chicago-based UAL's United Airlines and Houston-based Continental Airlines, which would be a bigger airline than Delta-Northwest in terms of traffic.
The clock is ticking to get any deals accomplished quickly, some observers say. That's because industry observers believe a combination has a better chance of surmounting the considerable political and regulatory hurdles under the current administration than under U.S. President George W. Bush's successor.
Delta and Northwest don't need a labor agreement between their pilots unions before announcing a combination, but having one in place now could help them speed up the integration of the two carriers down the line.
Much of the terms of how the combined carriers would operate had been resolved as of Tuesday, two people close to the talks said. The combined carrier would be based in Atlanta, and would be called Delta. Delta's chief executive, Richard Anderson, would be head of the new company, the people said.
It remained unclear what role Northwest's CEO, Doug Steenland, would play in the combined carrier, the people said. A combined Delta-Northwest would maintain a substantial presence in Minneapolis and there would be no furloughs for front-line U.S. employees, the people said. The two airlines have roughly 85,000 total employees.
Possible combination
The possibility of a Delta-Northwest combination has led Minnesota Gov. Tim Pawlenty to cancel an out-of-state trip.
Pawlenty was due to fly Tuesday to Las Vegas to address a renewable energy conference, but his spokesman said the trip was called off because of ""ongoing activities involving Northwest and Delta.""
Spokesman Brian McClung said the administration hasn't gotten any word that a deal is about to happen, but Pawlenty wants to ""be able to stay in direct contact with staff and commissioners in case his involvement is needed.""
The Republican governor said it's too soon to say if he'll fight the merger because he doesn't know what a combined Northwest-Delta company would mean for Minnesota. Northwest employs 11,500 people in Minnesota.