For many fliers Sunday, it was holiday travel woes, round two.

As of 2:30 p.m. ET, more than 1,800 U.S. flights were delayed and more than 150 were canceled, according to FlightAware.com.

The line for security screening at Chicago Midway International Airport on Sunday morning was so long that reporter Denise Whitaker of CNN affiliate KOMO measured it: 1.2 miles.

Traveler Sarah Crowder called it the worst she’s seen, prompting the Chicago Tribune’s Brian Cassella to call on the Transportation Security Administration to “do better.”

Sunday is one of the busiest travel days of the year, as millions of people return home after the Thanksgiving holiday.

“This happens sometimes,” Chicago Aviation Department spokeswoman Karen Pride said, according to CNN affiliate WLS. “There was a period of time earlier this morning, between 6 a.m. and 8 a.m., that lines were long because that is when most people are traveling for the holiday period.”

On Wednesday, the weather was widely blamed, as snow snarled traffic for parts of the country.

But conditions were much better Sunday in many areas, with “warmer and more tranquil conditions” in parts of the country including the East Coast, CNN meteorologist Todd Borek said. The temperatures were in the upper 40s in Chicago.

While a lot of attention goes to the airports — where the interconnected flight travel system can have a domino effect — the vast majority of Thanksgiving travelers hit the road.

Ninety percent of travelers were expected to go by road, AAA said, helped by the lowest gas prices in five years.

In all, more than 46 million people were expected to travel 50 miles or more for Thanksgiving, marking the highest volume since 2007.

“The average distance traveled this Thanksgiving will be 549 miles roundtrip and Americans will spend an average of $573 during the holiday weekend,” AAA predicted.