NEW YORK — Travelers braced for canceled flights, scrambled plans and holidays stranded in airports as a U.S. government shutdown threatened to snarl trips across the country.

News that the Federal Aviation Administration will reduce air traffic at 40 airports beginning Friday set off a flurry of worry among those planning trips.

“Oh no,” said 31-year-old Talia Dunyak, who is due to fly next week from Vienna to Philadelphia, among the airports targeted by the FAA for flight cutbacks. “I’m really hoping my flights don’t get canceled.”

Dunyak is due to meet her newborn niece, have some business meetings and celebrate Thanksgiving with family during a carefully planned trip. Now she’s wondering what will happen.

“It’s such a busy time to travel and there’s not so many direct flights,” said Dunyak, who works in public relations. “I might end up in some nightmare.”

Those worries were pervasive with Thanksgiving and the busiest travel days of the year looming ahead and a crush of passengers fearful of reliving a scene out of “Planes, Trains and Automobiles.”

Though the exact parameters of the FAA’s plan were not released, it promised to upend trips in broad swaths of the country. Affected airports are dotted across more than two dozen states and include some of the busiest hubs, including Atlanta, Denver, Dallas, Orlando, Miami, and San Francisco. In some of the biggest cities — such as New York, Houston and Chicago — multiple airports will be affected.

It was enough to cause Laura Adams to ditch plans of flying altogether.

Adams lives in Vero Beach, Florida, and typically flies with her husband for Thanksgiving with his family in Fair Hope, Alabama. They’ll now make a 10-hour drive instead.

“We really felt quite uneasy and just didn’t want to risk having a flight cancellation or a delay or getting stuck,” said Adams. “It just seems really risky.”

Though she’s not a fan of long car trips, she’s resigned herself to it, even if the shutdown ends and flights are restored.

“Just kind of weighing the pros and cons, it just seems like a better option,” she said.

Jennifer Dombrowski, a 45-year-old American living in Bordeaux, France, likewise adapted her plans. She’s due to travel next week to her hometown of Erie, Pennsylvania, for the first time in two years, and has opted to skirt U.S. airports altogether. She’ll fly to Toronto, then drive to visit her parents, including a father with terminal cancer.

“I don’t really want to deal,” she said.

Major carriers like United, Delta Air Lines and American Airlines said they would offer refunds to passengers who opt not to fly, even if they purchased tickets that aren’t normally refundable. And United Airlines said it would focus on cutting smaller regional routes.

Joseph Trainor, 55, who shuttles between New York and his home in Boynton Beach, Florida, every week, canceled his flights for next week — and is looking to book multiple backup routes farther down the road, in case future trips land on the chopping block.

“I’m afraid the flights I’m on are going to cancel,” he said. “It’s going to cause a cascading effect throughout the system.”

Even with the safeguards of additional reservations, Trainor knows cancellations can ripple through the system and affect him anyway. Still, he’s thinking about the Transportation Security Administration agents who have been going without pay in a shutdown that entered its 38th day on Thursday.

“They’re the heroes keeping the system going, and I don’t know if the government realizes how much air traffic and our economy is based on that,” Trainor said.