Every day, lingering government shutdowns cause flight delays and make flying “less safe.”

Washington Transportation Secretary Sean Duffy said on Friday that aircraft delays had resulted from air traffic controllers calling in ill on a daily basis during the federal government shutdown.

“Every day is different,” he said to reporters at a press conference held at Philadelphia International Airport. Air traffic controller personnel shortages account for an average of around 5% of our delays. Due to a lack of manpower, we have experienced delays of up to 53%.

Twelve air traffic control systems, including the control towers in Dallas-Fort Worth, Newark, and Phoenix; TRACONs that manage flights into and out of Houston, Newark, and Southern California; and centers that manage high-altitude flights around Albuquerque, Atlanta, Denver, and New York, were understaffed on Friday.

Since the shutdown began, 222 personnel shortages have been documented, which is more than four times as many as were reported during the same period last year. During the government shutdown, air traffic controllers, such as Transportation Security Administration screeners, must work but are not compensated.

According to Duffy, their salary will be a huge zero. “A lot of people are frustrated. Anxiety arises because, like everyone else, you anticipate receiving your income and make plans accordingly.

On October 28, controllers—roughly 10,800 government employees—will get their first payment of zero dollars. They got a partial payment on October 14 for the hours they worked prior to the closure, which was around 90% of the regular amount.

According to Nick Daniels, president of the National Air Traffic Controllers Association, the organization that represents controllers, the government funding shortfall makes air travel “less safe.”

“This system is less safe because air traffic controllers are not compensated for the essential work they perform during this shutdown, which causes needless distraction and makes it impossible for them to be fully focused on their work,” he said. “We’ll be less safe tomorrow than we are today, every day this shutdown lasts.”

According to Duffy, if an aircraft cannot be flown safely, the FAA will either slow it down or cancel flights.

“We will reduce the capacity of airplanes taking off and landing, or we will cancel flights, if we don’t have enough controllers, if we have controllers that are more stressed and less able to do the job,” Duffy said. “I don’t care as much whether you arrive on time. I’m concerned about your safety.

Control towers at Austin, Chicago-O’Hare, Nashville, Newark, and Reagan National Airport, as well as FAA facilities in Albuquerque, Cleveland, Denver, Fort Worth, Indianapolis, Los Angeles, Jacksonville, New York, and Washington, DC, all reported personnel shortages this week. Additionally understaffed were the airports in Chicago, Dallas, Detroit, Las Vegas, Philadelphia, and Houston that deal with planes coming into or leaving the region.

While future air traffic controllers enrolled at the FAA school will get compensation for the next several weeks, Duffy cautioned that the funds would soon run out, which would be “cataclysmic” for them.

Academy controllers and some individuals who were selected for the academy’s next class are leaving. “They’re leaving,” he said. “They’re asking themselves, ‘Why do I want to pursue a career where I could put in a lot of effort and possibly not get paid?'”

Approximately 3,000 additional air traffic controllers are needed nationwide, and the agency is attempting to “supercharge” recruiting by increasing academy enrollment.