CHICAGO (REUTERS) - Nearly three million people per day are expected to crowd into US airports over the holiday weekend, and millions more will fill the highways, as people head home to celebrate Thanksgiving.

By 5am, the lines were already long at Chicago's O'Hare airport, and officials say they're likely to stay that way through the weekend.

That's about 600,000 more than usual, and it's due to the improving economy, according to Beth Mosher with the American Automobile Association.