DENVER -- Major U.S. air carriers are offering discounted flights over the prime Thanksgiving and Christmas holidays.

Denver to Los Angeles over Thanksgiving, for example, is $200.

"It's not going to get much better than that. That's a fabulous fare," said Andrea Shpall, President of Polk/Majestic Travel Group.

Travel agents say a noticeable slowdown in air travel could be one of he reasons for fares that haven't been this low in 18 months, by some estimates.

"Right now, I'm seeing leisure travel being a lot more last-minute. I can see people saying,'Oh, flights are inexpensive. Maybe I will go visit my parents in Chicago after all. Maybe I will fly them out to Denver to have Thanksgiving with us," Shpall said.

A rare, one-way fare to LA is $79.

DIA to New York is $260, without taxes, and those relatively new baggage fees.

Falling oil prices have helped as well, coming down dramatically from their mid-summer peak.

Also Thursday, the Delta-Northwest merger was given final approval, sparking a rally for airline stocks, which closed up more than 11 percent as a group.

Travellers at DIA say the news is most welcome.

"Start having fun again ... People are fairly ... nervous and conservative about any spending. So, I think it's a good thing," said James Zeller.

Aviation analyst Mike Boyd of Evergreen said that all the major airlines, including Denver-based Frontier, should survive the end of the year and even turn a profit in 2009 thanks to greater efficiency and reduced seat capacity.