People took to social media to post photos of the line snaking through the main security area and into baggage claim.
Channel 2's Steve Gehlbach reported lines were over an hour long. Some travelers tweeted saying the lines were longer.
The south security checkpoint has been closed for a redesign to speed up the screening process.
The airport recommends travelers arrive two to three hours early if flying, especially on high-traffic days like Monday.
"Oh my God. I don't know if I'm going to make it because I have exactly one hour before my flight," said one traveler.