UPDATED: 12:53 p.m.
Flights at LaGuardia, Newark Liberty International and Philadelphia International airports were delayed Friday morning by less than an hour, on average, according to the FAA. Orlando International Airport and Hartsfield-Jackson Atlanta International Airport saw similar lags, the agency reported.
Staffing issues at air traffic control centers around Washington and Jacksonville, Florida, were blamed for delays across the Northeast, an official with knowledge of the situation told CNN.
The delays are directly attributable to the partial government shutdown, said Trish Gilbert, executive vice president of the National Air Traffic Controllers Association.
"You can't mess with a system that is so integral to the United States," she told CNN Friday. "This is reckless, what has been going on with the shutdown."
President Donald Trump has been briefed on the situation, his spokeswoman said.
Stoppage could have a nationwide ripple effect
Though all New York-area air traffic centers are fully staffed, delays continued at LaGuardia because of a ground stop, the official told CNN. The late-morning ground stop, ordered to clear congestion, has been lifted, the FAA reported.
Ground stops, especially long ones, typically can have a ripple effect nationwide, forcing bottlenecks and delays at airports that feed into other destinations.
Mary Campbell Jenkins said she was aboard a plane Friday on a tarmac in New York when the pilot announced that connecting flight information was limited "due to a ground stop here at LaGuardia due to the government shutdown."
The region is one of the most trafficked airspaces in the world, with 20% of all airline passengers in the country traveling out of airports in the Northeast, according to the FAA.
FAA officials were working Friday to mitigate the staff shortage, they said.
"We have experienced a slight increase in sick leave at two air traffic control facilities affecting New York and Florida," the agency said.
"As with severe storms, we will adjust operations to a safe rate to match available controller resources. We've mitigated the impact by augmenting staffing, rerouting traffic, and increasing spacing between aircraft as needed."
Controllers may be 'not fit for duty,' union exec says
The delays -- as the partial federal government shutdown marks its 35th day -- come less than two days after the president of a major air traffic controllers union warned that the ongoing shutdown poses a major safety risk.
Air traffic workers are making "routine mistakes" due to high levels of stress caused by the shutdown, Paul Rinaldi, president of the National Air Traffic Controllers Association, told CNN on Wednesday night.
"You cannot continue to operate a system this complex for this long without the support structure of the people that are furloughed," Gilbert told CNN Friday. "We are already short-staffed. Now, you have added the stress to air traffic controllers and their personal circumstances, and they're not sleeping at night. We are concerned that they are not fit for duty."
Flight delays are just one ancillary outcome of the shutdown that have affected air travel. The Transportation Safety Administration said callouts are double the rate of a year ago -- 7.6% versus 3%. TSA would not to reveal callout rates for individual airports. The airports with the longest average wait times were Atlanta with 42 minutes and Baltimore at 37 minutes.
Even before the shutdown, the FAA had identified the busy Northeast Corridor as a priority for improving its air traffic control infrastructure, targeting the region for planned improvements in communications procedures and efficient runway operations.
Air traffic controller staffing nationwide also already had been a key FAA consideration. The agency said in a 2018 report that it expected to lose "over 1,600 controllers due to retirements, promotions and other losses this fiscal year."