The petite middle-aged woman in a lavender sweater and tan chinos cleared the Midway Airport security checkpoint, but the outline of something in her carry-on luggage gave the screener pause.

A few moments later, a plainclothes policeman was rifling through her things.

“Do you have a firearm in your bag?” he asked.

“I completely forgot about that,” she said.

“Is it loaded?”

“Probably, yes.”

The gun was a fake, the woman a volunteer actor. But the scenario is real, Transportation Security Administration officials insisted, as the under-fire agency corralled two dozen or so reporters at Midway Thursday to demonstrate how “prohibited items” can contribute to the long security lines that have driven passengers to despair.

The TSA has come under intense criticism in recent days, after snaking security lines at O’Hare International Airport forced thousands of passengers to miss their flights.

Videos of similarly long lines at Midway have gone viral.

Volunteers posing as passengers move through the security line during a demonstration on TSA prohibited items at Midway International Airport on Thursday. | Ashlee Rezin/Sun-Times

Volunteers posing as passengers move through the security line during a demonstration on TSA prohibited items at Midway International Airport on Thursday. | Ashlee Rezin/Sun-Times

Four Chicago aldermen are pushing to have TSA workers replaced by private screeners at both airports.

On Thursday, TSA officials offered a demonstration. They sent 10 volunteers without prohibited items through security, then sent the volunteers back through — with one carrying a gun, another a water bottle and another with a knife in his bag. The first group made it through in about two minutes; the second group, six minutes.

“We’re not using this event to blame it on passengers,’ said Mark Howell, a regional TSA spokesman based in Atlanta. “But we wanted to illustrate that it is one piece of the puzzle. I’m not saying that infrastructure isn’t a problem. There are multiple things that factor into why wait times are growing.”

Faced with rising complaints across the country about long wait times, U.S. Department of Homeland Security Secretary Jeh Johnson said earlier this month that TSA plans to accelerate the 768 new security workers it had planned to bring on this year.

On Thursday, Howell said a 7-percent increase in air passengers nationwide since 2015 is a major contributor to the problem.

“We are going to continue doing what we are doing,” he said. “We’re not going to just let people walk through security. There is still going to be that process. What we have to work with now collaboratively is the more efficient way to do it.”

In the meantime, Howell warned passengers to be ready for a hectic summer.

“As you travel this summer, we ask everyone to plan like it’s a Thanksgiving Day or the Christmas holiday,” he said. “Because regular days within the summer are going to have the volume of those kind of days.”

Passengers wait in security lines at Midway Airport on Thursday. | Ashlee Rezin/Sun-Times

Passengers wait in security lines at Midway Airport on Thursday. | Ashlee Rezin/Sun-Times