Millions of Americans showed up at airports and train stations early Wednesday in hopes of getting a jump on what was predicted to be the largest Thanksgiving pilgrimage ever — despite rising gas prices and fears of air delays.

A record 38.7 million U.S. residents were expected to travel 50 miles or more for the holiday. Some were hoping to beat the evening rush on what is often called the busiest travel day of the year.

At LaGuardia Airport, check-in lines were beginning to build shortly before daybreak.

Sally and Neil MacDonald, of Sandy Hook, Conn., were flying from New York with their three children to Arkansas for a big family reunion.

“It’s too long to drive,” said Sally MacDonald at a crowded LaGuardia food court. “This gives us more time to enjoy family instead of having our three little kids in the car for 22 hours.”

She made her traditional pumpkin cheesecake for the feast, which she was carrying in a covered plastic pie plate.

“If they don’t allow it, I guess the airport security will be enjoying my pumpkin pie for Thanksgiving,” she said.

At the Salt Lake City airport, Dennis Tos made sure to try to avoid delays and crowds by boarding a redeye flight shortly before midnight.

“I specifically chose this hour to not get stuck in an airport. The horror stories kind of bothered me,” he said en route to a family reunion near Buffalo, N.Y. “I’ve never missed a Thanksgiving in the 58 years I’ve been alive.”

About 31.2 million travelers were expected to drive to holiday celebrations in spite of gas prices that were nearly 85 cents more per gallon than they were a year earlier, according to AAA. The national average for regular gasoline on Nov. 16 was $3.09 a gallon, up from $2.23 on Nov. 17, 2006.

“Wednesday ends up getting hairy,” AAA spokeswoman Christine Brown said. “Many people have to wait until after work to leave, and they’re competing with commuters as well.”

At New York’s Pennsylvania Station, travelers trickled into the station in the pre-dawn darkness. More than 20 people waited in line for the Amtrak ticket office to open.

Carrie Seligson wasn’t one of them. The 38-year-old construction worker bought her ticket in advance because she feared heavy traffic later Wednesday. She said she also got a better rate by booking a seat on one of the earliest trains to Washington, where she was going to spend the holiday with her family and attend her 20th high school reunion.

“I wasn’t sure what I was in for,” said Seligson, who arrived at the station an hour before her scheduled departure. “There are too many people later in the day, and the train gets too crowded.”

In Philadelphia, the scene at 30th Street Station was reminiscent of a normal weekday, with people scurrying to trains, plenty of open seating in waiting areas and none of the massive lines that sometimes curve across the station’s large concourse.

Shelly O’Connell, 49, of Philadelphia, was taking an 8:15 a.m. Amtrak train to Chicago to visit family, a trip she takes every year. She said she left home a little earlier this year in anticipation of heavy crowds at the station, but was pleased to see a relatively calm scene.

“I’m an old pro at this. I’ve got it down to a science,” O’Connell said.

Amtrak expected more than 115,000 riders on Wednesday, about a 70 percent increase over a usual Wednesday, spokesman Cliff Cole said. An electrical breakdown had snarled train traffic on the Northeast rail corridor over the weekend, but everything was running smoothly for the holiday, Cole said.

It wasn’t just the rails and roads that were expected to be crowded. Holiday delays at the nation’s airports have become such a fixture that President Bush last week called it “a season of dread.”

Bush announced steps to reduce air traffic congestion, saying the Pentagon would open two military air corridors to commercial airliners from Wednesday afternoon through Sunday, creating a “Thanksgiving express lane.”

Travelers heading to New York City area airports had special cause for concern, with a crush of 3,492 takeoffs and landings planned for Wednesday at John F. Kennedy International, Newark Liberty and LaGuardia airports. Delays at those airports have been getting steadily worse, and almost three of every four flight delays in the country can now be traced back to a problem in the greater New York area.

In all, about 4.7 million U.S. residents were expected to fly for the holiday, according to AAA.

At Dallas-Fort Worth International Airport, 23-year-old middle school teacher Kyle Martin waited anxiously in a security line early Wednesday morning, hoping to make a flight leaving for his family’s Chicago home. He had confirmed reservations for an afternoon flight, but decided to try to try to board an earlier flight on standby.

“If I can get through the line, I can make the flight,” he said.

He wasn’t optimistic of his chances. “You can see there’s already a security line, so I don’t think I’ll make the first flight.”

Denver resident Kevin Lillehei booked his flights with a 7-hour cushion in anticipation of flight delays, long lines and missed connections.

“It’s been very calm,” Lillehei said of Miami International Airport, after returning from a cruise in Antarctica with his wife, mother and sister. “Better than I anticipated, but I think it’s going to pick up.”

As for whether his return trip would be smooth, Lillehei said: “You always have to worry about snow and delays in Minneapolis, so getting back Sunday is going to be a hit or a miss.”

At least the weather seemed unlikely to cause any significant delays on Wednesday. Michael Musher, a National Weather Service meteorologist, said light snow in the Midwest and light rain elsewhere around the country could cause only minor problems.

AAA’s predictions for holiday travel are based in part on an online survey of U.S. residents, whose answers are weighted based on factors including education, income and geography. Participants are contacted via e-mail and elect to answer a questionnaire online.