CHICAGO (WGN) – A Ground Delay is in effect at Chicago O’Hare International Airport due to a shortage of air traffic controllers likely caused by the government shutdown.

The FAA said the delay is expected to take effect at 6 p.m. Tuesday. It is unclear just how long the Ground Delay will last, as one FAA website says the delay is in effect until 11 p.m. Tuesday, while another FAA site says the delay is in effect until 4 a.m. Wednesday.

local affiliate WGN-TV has reached out to Chicago’s Department of Aviation for comment, who directed us to reach out to the FAA. The FAA, however, is not responding to media requests due to the government shutdown.

The situation at O’Hare is mirroring a similar scene at other airports across the country.

Drew MacQueen is in charge of the Great Lakes Region for the union that represents air traffic controllers who are expected to work without pay until the shutdown is over, and air traffic control staffing shortages are starting to cause problems at airports across the country.

“Air traffic controllers didn’t start the shutdown and certainly air traffic controllers aren’t going to end the shutdown. That’s up to the politicians,” MacQueen said.

The FAA’s Operations Plan Advisory reports O’Hare has a staffing trigger until 4 a.m. Wednesday.

“It’s something that’s put in place to make the FAA aware that staffing levels are down a little bit, so they can take the appropriate measures to maybe slow down traffic to the level of staffing,” MacQueen said. “What they don’t need is the fatigue of dealing with that job while being short staffed, working six days a week, 10 hours a day. Now they’re worried about when they’ll get paid.”

That same “staffing trigger” reduced flights to and from Nashville International Airport (BNA) Tuesday afternoon. It’s a reduction that will remain in effect until further notice, according to BNA officials.

The problems first appeared Monday when the staffing shortages caused delays in Newark and Denver. In Burbank, California, no air traffic controllers were on duty in the evening, leading to average delays of two and a half hours.

“This is having great impact, great stress, great concern on our system,” Department of Transportation Secretary Sean Duffy said.

On Monday, Duffy said there had been a small uptick in controllers calling out sick. When there’s a staffing shortage, according to Duffy, the FAA reduces the number of takeoffs and landings to make sure the system isn’t overwhelmed.

“The system is fragile enough that even a small number exercising their right to have time off can have big effects and that’s what we’re worried about,” DePaul University Professor Joseph Schwieterman said.

Schwieterman, a transportation expert, also said the impact could be significant for airlines and passengers.

“Travelers need to be ready for contingencies,” he said. “You may want to make plans before you leave.”