The late crush of holiday travellers is picking up steam, with about 2.7 million US people expected to board flights on Wednesday and millions more planning to drive or take the train to Thanksgiving celebrations.

Airline officials say they are confident they can avoid the kind of massive disruptions that have marred past holiday seasons, such as the meltdown at Southwest Airlines over last Christmas.

And as of mid-day Wednesday that appeared to be the case.

US airports were reporting only five flight cancellations and 364 flight delays, according to FlightAware, a tracking service.

But snow showers could still snarl traffic in some parts of the country.

The National Weather Service was predicting accumulating snow in northern New England, including up to eight inches of snowfall in northern Maine.

Snow was also expected to hit the northern Rocky Mountains on Thanksgiving Day, bringing up to one foot of snow to parts of Wyoming by Friday.

Security queues at airports could be long.

Delta Air Lines is telling passengers to arrive at the airport at least two hours before their flight if they are traveling within the United States, three hours early if they are flying overseas, and maybe earlier on Sunday and Monday.

The Transportation Security Administration said it screened more than 2.6 million passengers Tuesday and it expected another 2.7 million passengers to come through airport security on Wednesday.

On Sunday, it expects to screen 2.9 million passengers, which would surpass a previous record set on June 30.

Queues ebbed and flowed all morning Wednesday at Moynihan Train Hall in New York.

Some travellers said they opted to travel by train for convenience or lower prices.

Others said they just wanted to avoid any chaos at the airport.

Matthew Hudnall and Abby Greenbaum were traveling from Atlanta to New York to Boston to visit family with their five-year-old daughter.

By the time they reach Boston, they will have taken a total of nine trains, they said.

“I think we thought it would be calmer and less stressful than flying. So, far that’s true,” Ms Greenbaum said.

Amtrak said passengers could see some boarding delays because of high passenger volumes this weekend.

The holiday will also test the Federal Aviation Administration, which faces shortages of air traffic controllers at key facilities that caused reductions in flights to the New York City area this summer and fall.

US Transportation Secretary Pete Buttigieg said during a news conference that the government prepared for holiday travel by hiring more air traffic controllers, opening new air routes along the East Coast and providing grants to airports for snowploughs and de-icing equipment.

Airlines have also added tens of thousands of employees in the last couple of years, and Southwest says it bought more winter equipment to keep planes moving even during sub-freezing temperatures.

AAA predicts that 55.4 million people will travel at least 50 miles from home between Wednesday and Sunday, the third-highest forecast ever by the car club.

AAA says most of them, 49.1 million, will drive.

Drivers will get a break from last year on petrol prices.

AAA says the nationwide average for petrol was down to 3.28 US dollars a gallon on Wednesday, compared with 3.63 US dollars a year ago.

Charging stations, not petrol prices, were on the mind of Guy Maughan as he set out last week in his Tesla on a 13-day Thanksgiving road trip that will take him from his home near Seattle to his brother’s home in Los Angeles and then to his parents in Phoenix.

Mr Maughan said he and his travel companion, a seven-month-old golden doodle named Nala, expect to spend only about 150 US dollars to charge the car along the 3,000-mile route.

“I love driving, I love road trips, and the car takes care of all the heavy lifting,” said Mr Maughan, who is a property agent.

“I just put in the destinations and it tells me where we’re going to stop. I’m thoroughly enjoying it.”

Air travellers will enjoy lower prices too. Airfares in October were down 13% from last year, according to government figures, and fares around Thanksgiving have been about 14% lower than a year ago, according to the travel site Hopper.

Even so, the high cost of rent, food, health care and other expenses were weighing on people’s travel plans.

Jason McQueary, a 25-year-old social worker and graduate student, said rent and other essentials eat up most of his pay cheque and he was grateful for his credit card points, which brought down the cost of his roundtrip flight from Denver to Chicago from 450 to 150 US dollars.

“I was just like, ‘Man, I’m glad I only come home once a year,’” said Mr McQueary, who was waiting to get picked up Tuesday after arriving to Chicago O’Hare International Airport to spend Thanksgiving with family in his hometown of Byron, Illinois.