(CNN) -- Millions of travelers headed home on one of the busiest days of the year Sunday, many of them fighting crowds but avoiding what had been feared could be even worse delays caused by treacherous weather.
A large storm system was moving through several eastern and central states, potentially causing significant problems on roadways big and small.
Flood warnings were in effect Sunday night for parts of Kentucky, Tennessee, Arkansas, North Carolina, Illinois and Indiana, and there were also flash flood watches for segments of Georgia and South Carolina -- according to the National Weather Service.
Drivers should be aware of changing conditions as rain could turn to snow showers Sunday evening, CNN meteorologist Bonnie Schneider said.
Still, such conditions did not appear to have a major effect on air travel -- at least as of 10 p.m. Sunday night.
New York's John F. Kennedy and Westchester County airports, as well as Teterboro Airport in New Jersey, had experienced delays earlier in the afternoon and evening, but the Federal Aviation Administration said there were no such problems later in the night.
Continental Airlines warned at 7:30 p.m. on its website that airports in and around Cleveland, Ohio; Detroit; and Memphis, Tennessee, may experience delays due to "reduced visibility and rain," but the FAA had no such reports two hours later.
At one of the nation's busiest airports, Atlanta's Hartsfield-Jackson International, a different kind of problem arose due to an aircraft with three blown tires on a runway, according to the FAA. In a news alert, the agency said there was a ground stop in effect, but video from the airport showed flights continued to land, and the FAA website showed no delays reported for Atlanta a few minutes later.
Cynthia Brough, a spokeswoman for AAA, said Sunday that anecdotal reports suggest that Thanksgiving holiday travel should be up from last year -- on par with the organization's report, released last week, that nearly 42.5 million would be in cars, planes and other modes of transport.
"This year, you had pent up demand from people who said they were tired of waiting for the U.S. economy to recover," Brough said. "So they are spending their travel dollars."
Slightly fewer people are choosing to get to their destinations by plane compared to last year. About 23.2 million travelers are flying during a 12-day period surrounding Thanksgiving, a 2% drop from last year, according to a forecast by the Air Transport Association of America.
Still, that doesn't mean there will necessarily be more space to spread out on flights, even with generally 20% higher fares than this time last year, according to the spokeswoman. Brough explained airlines "have been steadily cutting capacity all year long," meaning fewer available seats overall.
The busiest air travel days for the Thanksgiving holiday period were expected to be Sunday and Monday, the association said. Brough noted that, even if there are relatively few problems Sunday, bad weather could still impact air travel Monday.
CNN's Greg Botelho contributed to this report.