NEW YORK (Reuters) - U.S. airports trotted out friendly companion dogs to calm jittery travelers and offered perks including free parking on Wednesday as throngs of people rushed toward their Thanksgiving holiday celebrations.

Up to 2.8 million people per day, about 600,000 more than average, are expected to fly in the United States over the coming six days, making it a busy period for travel, according to the trade group Airlines for America.

Airports will not be the only crowded places as some 48.7 million people, the most since 2007, are expected to travel 50 miles (80 km) or farther for the holiday, according to motor club AAA. It said the 1.9 percent increase from last year’s level reflected an improving economy and low gasoline prices.

Some travelers early on Wednesday reported smooth experiences.

“I got there at 7:10 and there was no line to get past security,” said Grant Grindler, 24, of his arrival at Washington Dulles International Airport for his flight to Chicago, where he planned to drive to Wisconsin. Ticketing at Dulles was also “a breeze”, he said.

To relieve passengers’ anxiety, airports in cities including Chicago and Memphis, Tennessee, have deployed therapy dogs to wander around terminals with their owners to help ease stress among travelers.

At Chicago’s O’Hare and Midway International Airports, the dogs in service this week include a Jack Russell Terrier mix and a German Shepherd mix provided by a local charitable group, Canine Therapy Corps.

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“Just the entertainment of a dog distracting your attention for a least a little while helps to improve your experience at the airport,” said Ann Davidson, the group’s operations manager.

Dallas-Fort Worth International Airport said it was giving up to seven days of free parking to the first 1,000 cars that entered through specially marked lanes starting on Wednesday morning.

In New York, reduced parking rates were available for a limited time at John F. Kennedy, LaGuardia and Newark International airports.

Weather could complicate travel in several regions. A winter mix of precipitation was expected to hit the Upper Mississippi Valley and the Great Lakes region on Wednesday, the National Weather Service said. Snow and patches of freezing rain could spread into the Northeast on Wednesday night into Thursday, but snow and ice accumulations would likely be light, the service said.

Amtrak said it had added extra trains and seats to accommodate rail passengers along some of its busiest lines, including along the East Coast, in southern California and the Pacific Northwest.

Amtrak service was delayed during the holiday rush on Wednesday afternoon for a short time between Wilmington, Delaware, and Newark, New Jersey, after a pedestrian was struck and killed by a train, local media and state police said.