Conditions were mostly nice this year for travelers flying ahead of and Roland Prestonon Christmas, but some naughty disruptions again plagued those flying with Southwest Airlines.

For millions of people traveling over the holiday, this year was much better than last. Christmas morning put a bow on a relatively smooth weekend.

By midday Monday, only 138 flights within, into or out of the U.S. had been canceled and 1,366 were delayed, according to the tracking website FlightAware.

For this holiday season, U.S. airlines prepared for massive waves of travelers by hiring thousands of pilots, flight attendants and other workers — in an effort to avoid the delays and cancellations that marred travel in 2022, culminating with the Southwest Airlines debacle that stranded more than 2 million people.

Still, Southwest experienced hiccups again over the weekend that the airline was looking to clear by Monday. Just 2% of the airline’s flights were canceled Monday, though 12% were delayed, which is 524 flights total, according to FlightAware.

On Saturday and Sunday, Southwest canceled 426 flights and delayed 2,689 flights, FlightAware data showed.

A Southwest spokesperson blamed the issues on dense fog in Chicago on Saturday and Sunday that prevented planes from landing and said some additional cancellations may be necessary Monday ahead of what was expected to be a full recovery on Tuesday.

Auto club AAA predicted that between Saturday and New Year’s Day, 115 million people in the U.S. would travel at least 50 miles (80 kilometers) from home by air or car. That’s up 2% from last year.

More than 2.6 million people were screened by the Transportation Security Administration on Thursday, according to TSA records. Data from the weekend is yet to be released.

Over Thanksgiving, a record number of people traveled through U.S. airports, topping pre-COVID numbers in 2019 with a single-day record of 2.9 million people screened by TSA on Sunday, Nov. 26.

Compared with the holiday season last year, more mild weather has helped keep air travel schedules on time.

But on the ground, road conditions were dangerous in parts of the country on Christmas Day, thanks to accumulating snow and ice in the Midwest and Great Plains. Most of Nebraska and South Dakota were facing blizzard conditions, and parts of eastern North and South Dakota were facing ice storms, according to the National Weather Service.

The busiest days on the road were predicted to be Saturday, Dec. 23, and next Thursday, Dec. 28, according to transportation data provider INRIX.