Day after Christmas expected to be a travel nightmare, experts say AAA says that automobile travel on Thursday could take twice as long as normal.

If you are traveling the day after Christmas, expect some travel headaches.

According to Airlines for America, 2.9 million travelers are expected to fly on Dec. 26 and 27. That exceeds the 2.4 million who travel on U.S. airlines on a normal travel day.

Thursday will also be the worst time to be on the road according to the American Automobile Association. AAA projects that trips will take twice as long as normal in major U.S. cities.

An estimated 104 million holiday travelers are expected to drive to and from their holiday destinations from Saturday, Dec. 21 through Wednesday, Jan 1. That's the highest number on record.

"With kids out of school and many Americans taking extended time off for the holidays, drivers will experience only incremental delays throughout the week. Although congestion will be lighter than normal, knowing when and where major delays will likely happen will help save time and reduce stress this holiday season," said transportation analyst Trevor Reed in a post on the website of INRIX, a location-based data and analytics firm.

According to INRIX , here are the worst days to travel this holiday season and the peak congestion period in major U.S. cities:

- Atlanta, worst travel day: Dec. 26, peak congestion period: 4:30 - 6:30 p.m.

- Boston, worst travel day: Dec. 27, peak congestion period: 4:00 - 6:00 p.m.

- Chicago, worst travel day: Dec. 26, peak congestion period 4:45 - 6:45 p.m.

- Detroit, worst travel day: Dec. 26, peak congestion period: 4:30 - 6:30 p.m.

- Houston, worst travel day: Dec. 27, peak congestion period: 4:30 - 6:30 p.m.

- Los Angeles, worst travel day: Dec. 26, peak congestion period: 4:25 - 6:25 p.m.

- New York, worst travel day: Dec. 26, peak congestion period: 4:15 - 6:15 p.m.

- San Francisco, worst travel day: Dec. 26, peak congestion period: 4:00 - 6:00 p.m.

- Seattle, worst travel day: Dec. 27, peak congestion period: 4:15 - 6:15 p.m.

- Washington, D.C., worst travel day: Dec. 26, peak congestion period: 4:00 - 6:00 p.m.