CHICAGO (AP) — Chicago aviation officials say they expect more than 5.2 million travelers to pass through O'Hare and Midway international airports this holiday season.

The Chicago Department of Aviation said Tuesday that the number of travelers is expected to increase over last year's holiday season and passenger volume is projected to be the highest on record for Chicago's airports. The holiday travel season started Dec. 15 and goes through Jan. 4.

Aviation officials say they expect the busiest single day to be Friday, with 225,000 passengers at O'Hare and more than 70,000 passengers at Midway. Officials say more than 4.1 million passengers are expected at O'Hare throughout the holiday season, up 3.5 percent over last year. More than 1 million passengers are expected at Midway, up about 2 percent.