Westbrook residents John and Leah Thibault and their daughter, Autumn, 18 months old, stood Sunday among a pile of suitcases at the Portland Transportation Center waiting for the bus to Boston to catch a flight to spend Thanksgiving in Southern California.

This was Autumn’s first flight and her parents said they wanted to keep her experience as stress-free as possible.

“It takes a lot of planning, a lot of getting everything ready and checking the bags a million times,” said John Thibault.

The Thibaults were prepared for the busiest Thanksgiving travel season in years. AAA projects that 46.3 million Americans will hit the roads, skies and rails between Wednesday and Sunday, a 4.2 percent increase over last year and the heaviest level since 2007.

New England travel should mirror the national trend with a 4 percent increase over last year. A little more than 2 million New Englanders are expected to travel during the holiday.

Some troublesome weather could cause travel delays on Wednesday and Thursday. The National Weather Service office in Gray said there could be a mix of rain and snow Wednesday night and into Thursday morning as a storm moves up the East Coast. But meteorologist Chris Legro said Sunday it was still too early to be certain.

He said the rest of the holiday weekend should be quiet, with dry conditions and daytime highs in the 40s in southern Maine.

AAA said the lowest gas prices in five years are helping to fuel the increase in travel despite increases in airfares, car rental costs and lodging rates.

“This year, more Americans will give thanks for the opportunity to travel to friends and family than any year since 2007,” said Pat Moody, manager of public affairs for AAA Northern New England, in a prepared statement.

The vast majority of Thanksgiving travel will take place on roads, with 90 percent of travelers – or 41.3 million people nationwide and 1.8 million in New England – making their trips by automobile. Motorists will see average gas prices of $2.96 a gallon in Maine, $2.90 in New Hampshire and $3.09 in Vermont.

The Maine Turnpike Authority expects a 2 percent in increase in travel during the Thanksgiving holidays this year, said Erin Courtney, turnpike spokeswoman.

Last year 881,109 automobiles traveled the turnpike between Wednesday and Sunday during Thanksgiving week, with daily traffic peaking on the Friday after Thanksgiving at 190,280 automobiles.

About 3.55 million Americans are expected to travel by air, the highest since 2007.

The average distance traveled this Thanksgiving will be 549 miles round trip, AAA predicted, and Americans will spend an average of $573 on travel during the holiday weekend. AAA said room rates at its three-diamond rated lodgings have increased 8 percent over a year ago at an average $154 per night compared to $142 per night in 2013. Airfares are up about 1 percent over last year, with an average discounted round-trip rate of $189 across 40 top domestic markets. Weekend daily car rental rates, averaging $55, are up by 10 percent, AAA said.

Travelers at the Portland Transportation Center on Sunday offered various strategies to cope with crowds.

Ray and June Pokoski of Camden, who were headed to Austin, Texas, said they just try to go with the flow.

“We will lay back and just take it as it comes,” said June Pokoski.

Wearing the requisite ear buds, Spencer Burt, a Bates College student, said he was ready for the long trip home to Portland, Oregon.

“I just give myself enough time,” said Burt.

Foxcroft Academy sophomore Maria Cedeno was headed home from her school in Dover-Foxcroft to North Andover, Massachusetts, with her schoolmates, Oyku Ay, a sophomore from Turkey, and Nora Fleck, a senior from Germany.

“I just think of having fun with my family and friends,” said Cedeno.