On Friday evening, airports in Phoenix, Houston and San Diego were reporting delays because of staffing issues, and the Federal Aviation Administration warned that staffing problems were also possible at airports in the New York area, Dallas and Philadelphia.

A day earlier, flights were delayed at New York’s LaGuardia Airport, New Jersey’s Newark airport and Washington’s Reagan National Airport because of air traffic controller shortages. The number of flight delays for any reason nationwide spiked to 6,158 Thursday after hovering around 4,000 a day earlier in the week, according to FlightAware.com.

Many Federal Aviation Administration facilities are so critically short on controllers that just a few absences can cause disruptions, and Transportation Secretary Sean Duffy has said that more air traffic controllers have been calling in sick since the shutdown began. Early on in the shutdown, there were a number of disruptions at airports across the country, but for the past couple of weeks, there haven’t been as many problems.

Duffy said the disruptions and delays will only get worse next week after Tuesday’s payday arrives and “their paycheck is going to be a big fat zero.” He said controllers are telling him they are worried about how to pay their bills and frustrated with the shutdown.

“The stress level that our controllers are under right now, I think is unacceptable,” he said at a news conference Friday at the Philadelphia airport

The shutdown is having real consequences, as some students at the controller academy have already decided to abandon the profession because they don’t want to work in a job they won’t be paid for, Duffy said.

That will only make it harder for the FAA to hire enough controllers to eliminate the shortage, since training takes years. He said that the government is only a week or two away from running out of money to pay students at the academy.

“We’re getting word back right now from our academy in Oklahoma City that some of our young controllers in the academy and some who have been given spots in the next class of the academy are bailing. They’re walking away,” Duffy said. “They’re asking themselves, why do I want to go into a profession where I could work hard and have the potential of not being paid for my services?”

The head of the air traffic controllers union, Nick Daniels, joined Duffy. He said that already some controllers have taken on second jobs delivering DoorDash or driving for Uber to earn cash to help them pay their bills while the shutdown drags on.

“As this shutdown continues, and air traffic controllers are not paid for the vital work that they do day in and day out, that leads to an unnecessary distraction,” Daniels said. “They cannot be 100% focused on their jobs, which makes this system less safe. Every day that this shutdown continues, tomorrow, we’ll be less safe than today.”

Airlines and airports across the country have started buying controllers meals and helping them connect with food banks and other services to help them get through the shutdown.

The greatest concern is for new controllers who might make less than $50,000, but even experienced controllers who make well over six figures while working six days a week may be living paycheck to paycheck without much cushion in their budgets. Daniels said it’s not fair that controllers are facing impossible choices about whether to pay for rent or child care or groceries.

Duffy has said that air traffic controllers who abuse their sick time during the shutdown could be fired.

Republicans and Democrats have been unable to reach an agreement to end the shutdown that began on Oct. 1. The airlines and major unions across the industry have urged Congress to make a deal to end the shutdown.

Air Line Pilots Association President Capt. Jason Ambrosi said in a message to his members that he’s concerned about air traffic controllers and other federal employees.

“The safety of millions of passengers and tens of thousands of tons of cargo is in the hands of these workers. Worrying about how they’ll make their mortgage payment or pay for day care is an added stress they do not need,” Ambrosi said.

Rep. Sam Graves, who is Chairman of the House Transportation and Infrastructure Committee, urged Democrats to support the GOP bill to fund the government to help ensure the safety of the flying public.

“Our aviation system has operated safely throughout the shutdown, but it’s putting an incredible and unnecessary strain on the system, and on our air traffic controllers, flight crews, and many other aviation professionals,” said Graves, a Missouri Republican.

___

Associated Press airlines and consumer travel reporter Rio Yamat contributed to this report.