Air traffic controllers, pilots and flight attendants issued a stark warning about the safety of air passengers during the partial government shutdown, calling for the White House and Congress to find a solution.

“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 unions for all three groups said in a statement on Wednesday.

The longest-ever government shutdown, now exceeding one month, has left an estimated 380,000 federal workers furloughed, and forced another 420,000 to work without pay.

Air traffic controllers, Transportation Security Administration (TSA) agents, transportation security and law enforcement officers, safety inspectors, air marshals and FBI agents have all been caught up in the shutdown, leaving airports understaffed and raising questions about the current safety of the nation’s aviation system, according to the joint statement from National Air Traffic Controllers Association President Paul Rinaldi, Air Line Pilots Association President Joe DePete and Association of Flight Attendants-CWA President Sara Nelson.

Air traffic controllers and TSA screeners are among the federal employees who have been working without pay, because they were deemed too important to furlough. Many federal employees will miss their second paycheck on Friday.

The statement says staffing in air traffic control facilities is at a 30-year low, and hiring and training is frozen by the shutdown. In the interim, air traffic controllers are working overtime to keep airports running as smoothly as possible, the statement says.

Meanwhile, many airports have had to close security checkpoints due to TSA sickouts – with a growing number of TSA screeners not showing up for work due to the financial burden of working without pay.

The statement also said safety reporting data may be affected by strains on Federal Aviation Administration resources.

“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,” the union leaders said. “To avoid disruption to our aviation system, we urge Congress and the White House to take all necessary steps to end this shutdown immediately.”

That message was echoed Wednesday by five former Department of Homeland Security secretaries, who drafted a letter urging the Trump Administration and Congress to restore funding for the agency’s security, law enforcement and emergency preparedness work, which also extends to aviation security.

“We call on our elected leaders to restore the funding necessary to ensure our homeland remains safe and that the Department’s critical national security functions continue without compromise,” they wrote.

Among those to sign the letter was Trump’s former chief of staff, retired Marine Gen. John Kelly.

Get our Politics Newsletter. The headlines out of Washington never seem to slow. Subscribe to The D.C. Brief to make sense of what matters most. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Write to Jamie Ducharme at jamie.ducharme@time.com.