WASHINGTON >> The leaders of unions representing air traffic controllers and aviation safety inspectors warned today that the partial government shutdown was hurting the safety of the nation’s air travel system, another effort by the labor movement to press Washington to put federal employees back to work.

“Without a fully functioning FAA, a layer of safety is missing,” said Mike Perrone, national president of the Professional Aviation Safety Specialists, which represents safety inspectors who are furloughed.

At a rally outside the Capitol, where a crowd of air traffic controllers and other aviation workers gathered on a blustery afternoon to call for an end to the shutdown, Perrone warned of the risk of sidelining FAA workers who could be inspecting planes and pilots.

There is no clear-cut evidence that air travelers have been put in danger so far because of staffing changes caused by the shutdown. But the union leaders made the issue of safety a central part of their argument that the shutdown needed to end immediately.

“Every day that goes by that the government is shut down, safety is going to be compromised,” Perrone said. “Every day that goes by, something could occur that causes a crack in the system.”

Their show of concern on Thursday was among the most visible efforts by public employee unions to try to highlight the consequences of the shutdown and urge President Donald Trump and Congress to reopen the government.

At a rally outside the headquarters of the AFL-CIO, a short walk from the White House, hundreds of people, including federal workers and union leaders, also gathered to demand an end to the shutdown. They focused their blame on Trump and Republicans lawmakers.

“Shame on the Senate. Shame on the White House,” said Richard Trumka, the president of the federation. “This lockout has to end, and it has to end now.”

Workers said they were facing urgent financial pressure.

“I think from what I’ve saved up, I can last six months,” said Robert Reynolds, an aviation safety inspector who was been working for the FAA for 14 years. “It’s still going to hurt.”

The effort by unions to build pressure on the president and lawmakers to end the shutdown complements one in the courts that is focused on employees who are working without pay.

Last week, the American Federation of Government Employees filed a lawsuit claiming that the federal government was violating the Fair Labor Standards Act by not paying employees who were required to work during the shutdown.

Another union representing federal workers, the National Treasury Employees Union, filed a similar lawsuit this week. The union has also filed a lawsuit challenging the constitutionality of the federal law that allows the government to require some employees to work without pay during a shutdown.

With its constitutional challenge, the union is hoping to “establish, once and for all, a principle that will stop these shutdowns from continuing to occur in the future,” said Gregory O’Duden, its general counsel.

With some 800,000 federal workers affected by the shutdown, there has been no shortage of stories of personal hardship brought on by the funding lapse. Those stories are certain to continue as federal workers go unpaid.

But the public display by the aviation unions Thursday highlighted a strategy of generating concern among ordinary citizens that fundamental government services are being put in jeopardy.

News reports about Transportation Security Administration workers calling in sick during the shutdown have put a spotlight on one government service that, if significantly disrupted, would be immediately felt by the public.

The National Transportation Safety Board has been unable to investigate a dozen transportation accidents because of the shutdown. The accidents, including several plane crashes with a small number of fatalities, will be investigated after employees return from being furloughed, according to the safety board.

The FAA is also among the agencies whose funding has lapsed as a result of the shutdown, and the agency’s shutdown plan called for furloughs for about 18,000 of its 45,000 employees.

A long list of aviation trade groups and unions sent a letter to Trump and congressional leaders Thursday that cataloged the different areas where the FAA had been hobbled.

“This partial shutdown has already inflicted real damage to our nation’s aviation system,” the groups wrote, “and the impacts will only worsen over time.”

The FAA workers who have been furloughed include about 3,000 aviation safety inspectors, according to the Professional Aviation Safety Specialists. Their duties include performing oversight of commercial aircraft, pilots and maintenance facilities, as well as conducting in-flight and ramp inspections, according to the union.

“We can’t have the industry self-regulating,” Perrone said this week in an interview. He likened FAA inspectors to police officers parked on the side of a highway to deter drivers from speeding.

“Now we know the cops aren’t out there,” he said. As a result, he said, “Instead of 55, I’m doing 65. And tomorrow, maybe I’m doing 70.”

The union has urged its members to contact their congressional representatives to call for an end to the shutdown. A phone script suggests that union members explain that “our work is vital to the safety of the flying public” and say that their status, either furloughed or working without pay, “is causing stress for me and my family.”

Inspectors are taking their case to airports, too. Last week, some picketed at Miami International Airport, and one sign had a blunt message: “Was YOUR airplane properly inspected today? The Federal Aviation Administration does NOT know.” The inspectors union is planning pickets at other airports in the days to come.

Air traffic controllers are working, but not being paid, and support staff has been furloughed, according to the National Air Traffic Controllers Association. The FAA’s training academy in Oklahoma City has been shut down, leading to concerns about delays in bringing on new air traffic controllers.

The air traffic controllers’ association collected handwritten letters to deliver to lawmakers on Capitol Hill to inform them about how the shutdown is affecting air traffic controllers and their families.

“The last thing they need to be worrying about is how they’re going to pay the bills,” Jim Marinitti, a regional vice president for the union, said this week in an interview. “They need to be concentrating on separating airplanes, keeping the skies safe.”

In a letter last week to congressional leaders, the union’s president, Paul Rinaldi, took issue with the absence of support staff. “We wouldn’t ask a surgeon to perform an operation without the assistance of a support team,” he wrote, “and we shouldn’t be asking air traffic controllers to continue working without support staff.”

The FAA says travelers should not be worried. Inspectors who are furloughed are being called back to work as they are needed, the agency says.

“The traveling public can be assured that our nation’s airspace system is safe,” said Greg Martin, a spokesman for the FAA.

“We are allocating FAA resources based on risk assessment to meet all safety critical functions,” he added. “We continue to proactively conduct risk assessment, and when we identify an issue, we act and recall our inspectors and engineers, as appropriate, to address them.”