It's not unusual for airport security agents tasked with screening passengers to call-out sick in noticeable numbers after the holidays.
But with a partial government shutdown entering its third week — and threatening to deny the nation's 51,000 Transportation Security Administration employees involved in the screening process a paycheck come Friday — the idea that more and more agents might be no-shows at checkpoints could have a cascading effect throughout airports and lead to longer lines.
Such an outbreak has been dubbed a "blue flu" — in reference to the blue shirts that TSA agents wear.
More from NBC News:
Hard to digest: Inmates eat holiday steak during shutdown while prison workers go unpaid
Winners & losers: Past government shutdowns and how they ended
Prolonged shutdown could leave millions without food stamps and hit small businesses
"If you don't have a check to pay your bills, what are you going to do?" said Rudy Garcia, president of the American Federation of Government Employees 1040 local, the union for Dallas TSA employees. "You will look for something outside of what you're doing now."
On Friday, about 5.5 percent of the TSA workforce called out at Dallas/Fort Worth International Airport, compared with 3.5 percent on a normal day,
And at John F. Kennedy International Airport in New York, a TSA employee union official told CNN last week that up to 170 of its workers have called out.
Bilello denied in a statement Sunday that there was any significant uptick in call-outs and that they are "a normal occurrence this time of the year."
Long lines on a weekend after the holiday season are also common, TSA officials said.
But agents, many of whom make about $30,000 a year, say they don't want to feel like their livelihoods are in limbo as the Trump administration and Washington lawmakers fail to end a federal shutdown that is affecting everything from food stamps to immigration courts. Both sides have been at an impasse over the White House's demands for funding a wall at the U.S.'s southern border.
"We are a paycheck to paycheck family," said Brian Turner, a Philadelphia TSA officer for six years, adding that "we have a mortgage payment. We have credit card payments. We have car payments. Utilities. And we also have childcare. So with half of our income gone, it is very concerning."
Other airport workers, such as air traffic controllers, are also set to work without pay as the shutdown drags on and their next paycheck is due Jan. 15. The Federal Aviation Administration said there have been no widespread reports of controllers calling in sick.
Still, without the promise of a next paycheck, workers such as Turner will be left to decide whether to take matters into their own hands and look elsewhere for employment.
"I have to keep food in the kitchen," Turner added. "And I will have to make that call at some point."