Thanksgiving getaway sees 43m Americans hit the road
An estimated 43 million Americans are travelling on Thanksgiving eve, amid bad weather and transport union action.
Fog in Chicago grounded 200 flights, heavy rainfall drenched the US Pacific Northwest, and train services were disrupted in New York City.
In Los Angeles, union workers staged a protest near the city's main airports, with some arrests reported.
Thanksgiving, a hugely popular holiday, celebrates the Pilgrims' first harvest in what is now Massachusetts state.
For the 39 million Americans travelling in vehicles, heavy traffic was expected in New York, Chicago and Los Angeles.
But there was some good news for motorists: the national average price for petrol was down $0.28 (£0.18) cents per gallon from a month ago, according to the American Automobile Association (AAA).
Workers at Los Angeles International Airport marched in a dispute over contracts and health insurance benefits.
A sit-down protest staged at about 13:15 local time (21:15 GMT) prompted several arrests, the Los Angeles Times reported.
Picketing was also reportedly planned by airport workers at Chicago's O'Hare, New York's JFK and Florida's Fort Lauderdale.
In New York, a switch failure caused a break in train services at the city's Penn Station on Wednesday evening, with nobody allowed to enter the station as officials battled to manage crowds.
After being hit by the recession, Thanksgiving travel returned to 2007 levels last year, according to the AAA.
In 2012, the number of Americans travelling at least 50 miles (80km) between Wednesday and Sunday was expected to increase to 43.6 million, which would be up 0.7% from last year.
Obama turkey pardoning
Those heading out over the holiday are flying less, driving more and covering shorter distances, says the AAA.
At the White House, President Barack Obama carried out the traditional US presidential duty for Thanksgiving: pardoning a turkey.
"Tomorrow, in the company of friends and loved ones, we will celebrate a uniquely American holiday," Mr Obama said.
"And it's a chance for us to spend time with the people we care about and to give thanks for the blessings that we enjoy; and to think about just how lucky we are to live in the greatest nation on Earth."
Since taking office, he has created his own custom of sparing an extra turkey.
This year, Mr Obama showed mercy on Cobbler and Gobbler, who will live out their days on George Washington's estate in Mount Vernon, Virginia.
Forty-six million other turkeys will not be so lucky - that is how many of the poultry are expected to be consumed across the US on Thursday.
Thanksgiving will be a more low-key affair for those New Yorkers still recovering from the effects of the recent super storm, Sandy.
Mr Obama touched on the storm's impact in his remarks, saying Thanksgiving is "also a time to remember those who are less fortunate - and this year, that's particularly true for our neighbours in the North-East who have lost their homes and their possessions, and even their loved ones to Hurricane Sandy".
Macy's department store has set aside 5,000 seats along its Thanksgiving Day Parade route for families affected by the deadly cyclone.
And Occupy Sandy, the storm-relief offshoot of the Occupy Wall Street movement, will host a Thanksgiving dinner in lower Manhattan.
Retailers are also preparing for Black Friday, the day after Thanksgiving that is traditionally the busiest shopping day of the year.