Passengers ABC7 spoke with Thursday morning said they aren't feeling too optimistic about federal lawmakers being able to hash out a deal before the weekend.
The FAA now says hundreds of thousands of passengers could be affected if the government shutdown continues.
It was business as usual inside O'Hare's Terminal 1 Thursday morning with no major delays and only a handful of cancellations. But in the hours ahead, it could be a much different story.
"Air traffic controllers are showing up to work every day to deal with Issues that we've never seen before. 36-day shutdown," Nick Daniels, president of the National Air Traffic Controllers Association. "The stresses, the pressure, the fatigue is setting in."
As the government shutdown continues on its record-break streak, the FAA now says flight capacity will be cut by up to 10 percent at 40 major airports across the country - including Chicago's O'Hare and Midway airports.
Passengers are now bracing for potentially thousands of delays and cancellations unless the shutdown is averted.
Air traffic controllers and TSA officers have been unpaid for six weeks and are increasingly calling out sick, straining air travel.
"I can't imagine going without multiple paychecks," Dan Dempsey, who is traveling to Mexico, said. "Certainly that's going to put a pinch on people. I think it just highlights the things we have to figure out."
Lombard's Dan Dempsey is traveling to Mexico for a week.
"I got faith that this might be the last push we need get some things going in Washington and get this figured out," Dempsey said.
"I fly for work," Kurt Spiering, who is traveling to Denver, said." I fly all the time. I get here 45 minutes a flight. Today, I got here two hours before my flight."
Chicago's Kurt Spiering is flying to Denver and is keeping his fingers crossed about getting home Saturday. He said he is not optimistic about a deal this weekend.
"It's ridiculous," Spiering said. "I don't know why they can't get a deal done."
In a message to employees, United CEO Scott Kirby reassured anxious passengers, writing in part..."...any customer traveling during this period is eligible for a refund if they do not wish to fly - even if their flight isn't impacted."
The CEO of Frontier Airlines told passengers to have a back-up ticket on another airline, "If your flight is cancelled, your chances of being stranded are high..."
Fora Travel's Susie Turek has this advice for folks getting ready to board a flight in the hours ahead.
"I would also say to make sure travelers are keeping their airlines' apps close at hand for real-time updates and if there is an option if people have flights coming up to get travel insurance," Turek said.
Sources tell ABC News the FAA will begin cutting four percent of flights Friday and ramp up to 10 percent this weekend if the government shutdown continues.
Late Thursday, United Airlines released a full list of flight cancelations through Sunday.