BISMARCK, N.D. — A planned boycott of airport security scanners was a bust, but holiday travelers in the western U.S. had to contend with a chaotic mix of snow, sleet and ice.

The powerful storm system closed roads and delayed flights from Anchorage to Salt Lake City, and promised to bring messy wintery weather to much of the Dakotas on Thanksgiving Day. Freezing rain glazed roads across the Midwest, and at least three traffic deaths in Iowa were blamed on the weather.

But the cascading delays and monumental lines that many feared would result at airports from the so-called National Opt-Out Day didn’t materialize Wednesday, one of the busiest travel days of the year.

The loosely organized Internet campaign encouraged travelers to protest new security screening by boycotting body scanners that can see through people’s clothing and insisting on the more time consuming pat-downs. But few passengers seemed to heed the call.

“It was a day at the beach, a box of chocolates,” Greg Hancock, 61, said after going through a body scanner Wednesday at the Phoenix airport. He was sent through the scanner after a golf ball marker set off the metal detector.

His wife, Marti Hancock, 58, said that ever since she was in the air on Sept. 11, 2001, and feared there was a bomb on her plane, she has been fully supportive of stringent security: “If that’s what you have to do to keep us safe, that’s what you have to do.”

Some protesters showed up, including one man seen walking around the Salt Lake City airport in a skimpy, Speedo-style bathing suit. At other airports, they carried signs denouncing the Transportation Security Administration’s screening methods as unnecessarily intrusive and embarrassing.

By most accounts, though, the lines moved smoothly, and there was no more or less congestion at major U.S. airports than in previous years on the day before Thanksgiving.

“I would go so far as to say that National Opt-Out Day was a big bust,” said Genevieve Shaw Brown, a spokeswoman for the travel company Travelocity, which had staff at 12 of the nation’s largest airports watching for problems.

Protest organizers — some of whom had no plans themselves to fly on Wednesday — were not prepared to declare the event a flop, saying the publicity alone cranked up pressure on the White House and the TSA to review their security measures.

The TSA maintains that the need for such measures was demonstrated last Christmas, when a Nigerian man allegedly tried to blow up a Detroit-bound plane with explosives hidden in his underwear.

More than 40 million people plan to travel over the Thanksgiving holiday, according to AAA, with more than 1.6 million flying — a 3.5 percent increase from last year.

Some travelers who opted for the ground said they did so in part because of anticipated headaches at airports, but they were delayed anyway by the weather. Early-season snowstorms buried Seattle, and shut down highways for a time in Idaho, Wyoming and Utah. It also brought strong winds Wednesday from New Mexico to Missouri.

At an Amtrak station in Chicago, Pam Edwards said she decided to travel by train from Jackson, Miss., even though it would take 15 hours instead of two.

“With all the things with the TSA, I just decided it might be a little bit easier, stress-wise, to take the train,” the 61-year-old retired preschool teacher said as she stepped off the train.

Marie Martin, taking a break at a gas station in Oklahoma City during her family’s road trip from Arizona to Georgia, noted that it was “a lot cheaper for a family of five to drive rather than fly,” but also said it eliminated the hassle of flying.

“You don’t have to deal with the crowds. You don’t have to deal with the baggage check-in,” she said. “You don’t have to deal with the pat-downs.”