One of the quirks of American politics is that conservatives and libertarians can use regular shutdowns as evidence that the federal government was never really that necessary in the first place.

But 420,000 federal workers are still working, without pay, holding off a short-term disaster. At the Food and Drug Administration, for example, semi-annual factory inspections are on hold. But Department of Agriculture meat plant supervisors are still working.

In the bracket of workers whose absence would constitute a national crisis, top seed must surely go to the 51,000 employees of the Transportation Security Administration. The TSA may practice intrusive security theater, but in its absence, commercial air travel in the United States would grind to a halt, creating global transportation chaos.

Like other federal workers, TSA agents missed their first paycheck on Friday. More and more agents are calling out sick, either in protest or to make up for lost wages.

On Saturday, 5.6 percent of officers called in sick—up from 3.3 percent a year ago. TSA head David Pekoske announced $500 bonuses. Over the weekend, airports in Houston and Miami shut down terminal checkpoints in an effort to better distribute shrinking staffs.

On Monday, 7.1 percent called in sick—up from 3.1 percent a year ago, according to the agency. Wait times at the main checkpoint at Atlanta’s Hartsfield-Jackson, the nation’s busiest airport, were over an hour long on Monday morning.

The American Federation of Government Employees, the union that represents the 44,000 TSA screeners, has sued the federal government on their behalf. The attrition caused by the shutdown, the TSA union rep said last week, “will create a massive security risk for American travelers.” The median TSA screener makes $40,000, according to the Bureau of Labor Statistics, and the starting salary is $15 an hour.

In the New York Times, Barbara Ehrenreich and Gary Stevenson make the case that it’s time for TSA workers to strike. That would be illegal, but the situation they find themselves in—working without pay for weeks at a time—is without precedent.

Other quieter consequences of the shutdown are no less devastating. But a meltdown at the airports would put a new level of pressure on Republicans to reopen the government. Fewer than one in four American adults fly more than twice each year, according to research by Ipsos. But those who do tend to be wealthy and influential, and closing the nation’s airports would make federal workers’ misery their own.