With just less than two weeks to go for Christmas, U.S. travelers are all set to hit the roads, rails and skies for the long-awaited winter holiday. 

Air travel has been the most favorite mode of transport of U.S. travelers, enjoying an increased share of holidaymakers for five consecutive years. 

This year, U.S. airlines are expecting a 5.2 percent increment in air travel with over 2.5 million travelers per day during Christmas and New Year's break, Associated Press reported.

The last working Friday before Christmas is usually the busiest Friday of the year, and also the day people set out in droves for Christmas travel.

Trade group, Airlines for America, forecasts a 45.7 million passenger volume for U.S. airlines during the 18-day holiday from December 20 to January 6, though the largest share of travelers will still be on the road.

About 143,000 seats have been added per day on both domestic and international flights since last Christmas. Yet that may still lag behind the mobility needs of the estimated passenger growth, approximately 126,000 passengers per day, according to the group.

Travelers seeking cheapest flights should start journey on Christmas Eve and Christmas Day, when most people opt to stand on the ground and immerse themselves in the festive atmosphere.

(With inputs from the Associated Press)