Elected officials and union leaders on Thursday warned of growing risks to the nation’s aviation system as the partial government shutdown threatened to stretch into a second month and workers face the prospect of another pay period without a check.

“The truth is that Americans who are flying today are less safe than what our standards have been,” Sen. Mark R. Warner (D-Va.) said as he stood with a group that included air traffic controllers, flight attendants and aviation safety specialists at an event at Reagan National Airport.

Union leaders said the nation’s aviation system works because it is multilayered, and while many workers remain on the job, others who perform critical functions have been furloughed and their absence leaves the system — and those who use it — vulnerable.

“Are we less safe today? We are less safe,” said Sara Nelson, international president of the Association of Flight Attendants. “The critical networks of layers of safety and security are not in place because we have people furloughed who fill those roles,” Nelson said. “As flight attendants, we know what happens when there is a gap in security.”

An estimated 800,000 federal employees are furloughed or working without pay during the shutdown. Agents with the Transportation Security Administration and air traffic controllers and others with the Federal Aviation Administration are among those working without pay.

A growing number of TSA officers are staying home because they cannot afford the costs of working free. The number of TSA employees failing to show up hit 10 percent Sunday and was 7.5 percent Wednesday, the agency said. Some airports, including Baltimore-Washington International Marshall Airport, have had to temporarily shut down checkpoints and redeployed officers to cover the gaps. Others have set up food pantries to assist their federal workers.

Warner said it was unconscionable to expect federal workers to continue to work free.

“The fact is, maintaining the air-traffic safety and volume of air traffic coming into our airports is stressful enough work on its own without having to spend 30 percent of your time worrying about how you’re going to pay the mortgage or your kid’s tuition,” Warner said.

Sen. Tim Kaine (D-Va.) said images of federal workers waiting in food lines hark back to the photographs captured by Dorothea Lange of bread lines during the Great Depression.

“Why is our country treating our people like this?” Kaine said. “This is a completely self-inflicted wound that the president has inflicted, but I guess I’ve used the wrong word — self-inflicted — because [Trump’s] not damaging himself, he’s just damaging a lot of other people because he can’t get his way.”

Warner said the consequences of the shutdown go beyond government employees and contractors.

“Staff and resource shortages lead to flight delays and cancellations, which hurts travelers, businesses and the regional economy,” Warner said.

Rachael Abraham, a TSA employee who is president of the American Federation of Government Employees Local 1142, said morale has steadily declined, with workers increasingly worried about how to pay for essentials like gas to get to work, groceries and child care.

“We’re forced to get up at 2:30 in the morning, some of us earlier, to figure out how we’re going to get gas for our cars to get to and from work, and figure out child care when we have no income coming in,” she said. “We’ve become the bottom of the heap.”

FAA officials on Thursday sought to reassure the public that the nation’s skies remain safe.

“Overall, the traveling public can be assured that our nation’s airspace system is safe,” an FAA spokesman said. “Air traffic controllers and the technicians who maintain the nation’s airspace system continue to work without pay as they fill a critical mission to ensure the public’s safety. We sincerely thank FAA employees — especially the dedication and professionalism of our air traffic controllers, technicians and inspectors — who are working to keep the traveling public and our skies safe.”

Unlike the TSA, the agency said, there has been no unusual increase in absenteeism among air traffic controllers and there have been no operational disruptions due to staffing. “We have not observed any appreciable difference in performance over the last several weeks compared to the same periods during the previous two years.”

It added that there has been no measurable increase in unplanned retirements or resignations.

The National Air Traffic Controllers Association (NATCA) has vowed throughout the shutdown that its people will comply with federal mandates and continue to work without pay.

Union spokesman Doug Church batted down reports Thursday that its members might walk out, using a single sentence: “It is illegal.”

But at Thursday’s event, NATCA President Paul Rinaldi warned of growing strains on front-line workers.

“We have built a system over the last 10 years of layers of safety net,” Rinaldi said. “Over the course of the last 34 days, that net is deteriorating, and I keep telling people, and I don’t know when, but I can see the unraveling happening. I can see the controllers more concerned — ‘I guess I can work, but I’m reaching my limit.’ ”

He also pushed back against the FAA’s contention that the shutdown is not compromising safety standards.

“Why bring back safety professionals if there’s no risk in the system?” he said.

The FAA began to recall safety inspectors two weeks ago, saying they include those who do flight field inspections, evaluate and audit, provide certifications, handle accident investigations and do oversight for commercial space launches.

Workers also are stressed and tired from working second jobs to make ends meet, he said, which leads to mistakes.

“I’m starting to see as I get the safety reports every day — routine mistakes and clearances being made because controllers are distracted,” Rinaldi said. “They are distracted and you cannot have them distracted.

“The maximum they can work is a 10-hour, six-day workweek,” he said. “They are all maxed out on that. Then they are figuring out, I have to go drive Lyft or Uber before work and after work. They are not mitigating their fatigue, they are coming to work stressed because they can’t pay the bills and at the same time fatigued because they are working around the clock to try to make ends meet.”

Leroy McCray, an air-traffic systems specialist who maintains navigation systems at National Airport, said he’s seen both the financial and emotional strain on his colleagues. Morale, he said, is low and some are starting to get angry.

“People need to realize that not getting paid to come to work is un-American,” he said.

Thursday’s event at National came a day after a coalition of unions said a breakdown in the aviation system was inevitable if the shutdown continues.

“We have a growing concern for the safety and security of our members, our airlines, and the traveling public due to the government shutdown,” said a letter signed by Nelson, Rinaldi and Joe DePete, president of the Air Line Pilots Association. “In our risk-averse industry, we cannot even calculate the level of risk currently at play, nor predict the point at which the entire system will break. It is unprecedented.”

The letter went on to say: “As union leaders, we find it unconscionable that aviation professionals are being asked to work without pay and in an air-safety environment that is deteriorating by the day. To avoid disruption to our aviation system, we urge Congress and the White House to take all necessary steps to end this shutdown immediately.”

Workers, too, said they would like to return to the days when they did not have to worry about getting paid.

“Why are we at this point right now?” said Abraham, the TSA worker. I want to continue to work. I love my agency. My management has been great with us, but there’s only so much they can do because they aren’t getting paid.”