NEW YORK - Tens of millions of Americans returning home after the long Thanksgiving holiday weekend Sunday had cooperative weather and mostly efficient airport operations to thank for smooth traveling conditions.

Besides a winter storm that was to bring freezing rain and snow to the central Plains on Sunday night and into Monday, weather across much of the country is seasonably mild, said National Weather Service meteorologist Bruce Sullivan.

"Enjoy it while it lasts," he said.

Most airports across the country were running with delays of 15 minutes or less, according to Federal Aviation Administration air traffic control system data. But a large volume of passengers at Dulles International and Reagan National airports in Washington, as well as LaGuardia in New York, led to slightly longer delays, the data show.

In Atlanta, officials are projecting 88,000 travelers to pass through the world's busiest airport by the end of Sunday, making it their busiest travel day of the year. A spokesman for Hartsfield-Jackson International Airport says the prior record for the year was 80,000 people on Columbus Day.

Lobbying group Airlines for America estimated more than 25 million passengers would take to the sky on U.S. airlines during the 12 days surrounding Thanksgiving.

And the motoring group AAA estimated that nearly 47 million Americans were expected to travel at least 50 miles from home via car, plane or bus over the weekend - the highest number since 2007.

At Pennsylvania Station in New York City, college junior Seth Greenspan said the normally chaotic transit hub appeared strangely calm as he awaited an Amtrak train back to the College of William & Mary in Virginia after spending Thanksgiving on Long Island.

"Amtrak itself can be unreliable, whether or not it's a holiday," he said ahead of an eight-hour trip. "So far it seems OK."

Toni Baines and her husband, Marlon, who spent Thanksgiving in the Bronx and were head back to their home in Richmond, Va., said it appeared transit officials anticipated an influx of travelers and planned accordingly.

"They've been running a lot of extra trains," she said. "So far we haven't had any problems."

In California, transportation officials reported only some fender benders slowing traffic. Caltrans spokeswoman Lauren Wonder said people may have chosen to return from Thanksgiving trips on Saturday - as she did - leaving Sunday as a free day before work. She also suggested people may have decided to stay home for what she called a "stay-turkey-cation."