WASHINGTON, D.C.: A shortage of air traffic controllers caused more flight delays across the country at the start of the week, as controllers faced their first missed paycheck during the ongoing federal government shutdown.

The Federal Aviation Administration (FAA) said on October 27 that staffing shortages led to average delays of 20 minutes at Dallas Airport and 40 minutes at both Newark Liberty and Austin-Bergstrom airports. In Austin, there was also a brief ground stop, meaning planes were not allowed to take off for a short time until the FAA lifted the restriction around 4:15 p.m. local time.

The FAA also warned of possible staffing problems at its Jacksonville, Florida, facility, which could cause more disruptions.

Transportation Secretary Sean Duffy warned last week that flight delays and cancellations would likely increase as air traffic controllers continue to work without pay during the shutdown, which has now lasted almost a month.

Speaking on Fox News' "Sunday Morning Futures", Duffy said more controllers were calling in sick because of financial stress. "That's a sign they're getting worn out," he said.

At Los Angeles International Airport (LAX), one of the world's busiest airports, flights were briefly delayed again, a day after the FAA issued a two-hour ground stop there because of a controller shortage. According to Cirium, an aviation data firm, only 72 percent of Sunday flights at LAX departed on time.

Most controllers are working six days a week with mandatory overtime but no pay, according to the National Air Traffic Controllers Association (NATCA). Many cannot take side jobs because of the heavy workload and have started taking sick days instead.

On October 28, union members gathered at major airports, including New York City and Atlanta, to hand out flyers explaining how the shutdown is hurting aviation safety and the workers who keep the system running. This comes as they miss their first full paycheck since the shutdown began.

Some U.S. airports have stepped in to donate food and other help to unpaid FAA and TSA workers.

Even before the shutdown, the FAA was already short by about 3,000 controllers. NATCA President Nick Daniels said staffing levels are now the lowest in decades, with only about 10,800 controllers working nationwide.