Hundreds of flights were already canceled Thursday morning as a winter snow storm moves into the Chicago area.
Passengers should expect more flight issues from the storm, with impacts across the country.
O'Hare Airport reported 569 flight cancellations as of 9:30 p.m., with 260 flight cancellations at Midway Airport. Both airports had delays of about 15 minutes.
By 9 a.m., O'Hare was slammed with passengers waiting in long security lines and waiting for word on if they could even get out of town.
"Our flight got canceled at 8 o'clock this morning, so my husband is going to try and get us on another flight, but if not, we have to rent a car," passenger Alex Gagel said. "It's an extra $500 to rent a car, so it's going to be hard"
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Kathy Pelka and her family are heading west to Orange County and have been watching the board all morning in hopes of leaving sometime soon.
"We were supposed to leave on Friday, but we updated it to today," Pelka said. "Now it's pushed back to 11:45 so we're just hoping we get on the plane"
On Thursday, travelers were shifting plans, either voluntarily, or because airlines are canceling and rescheduling flights.
By late evening there was a much calmer crowd at O'Hare.
"I have been refreshing my app like every 30 to 40 seconds, just to see if it's on time," said Kirstin Edmonds, who is traveling to Germany. "You always have to be ready for the unpredictable, things can change in a second in this."
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With around one in four of all arriving and departing flights canceled, thousands of those expected to go through the airport stayed home on what was originally projected to be the busiest air travel day of the holiday weekend.
A pair of newlyweds passed the time with a game of Uno until their departure for a honeymoon in Italy.
"We got to the flight a bit early. We don't leave until 9 p.m. We wanted to get ahead of the blizzard. We're from Milwaukee; family was here, had lunch, told them to drop us off after lunch," Joe Williams said.
"This was a total surprise, got a text this morning to get ready to go to London, so I packed my bags and here I am. That's amazing!" traveler Mildred Bond said.
Iowa native Kathleen Schmidt is connecting in Chicago on her way back from Europe. She arrived Wednesday night.
"We thought we'd save time and fly somewhere closer to home, and now our flights have been canceled twice, home to Iowa. Fortunately we have my daughter here to stay, so now we're waiting for my daughter to come for us a second time," Schmidt said.
And while the airlines sent out notices allowing passengers to reschedule days ago, there are still those who have not yet managed to change their flights.
Silvia Diaz's flight to Peru isn't until Friday, but she was at O'Hare Thursday on the phone with United, hoping they can find her an early spot out.
"I'm trying to get on a plane today and wait in Orlando. How many hours I don't know, but at least I'm out of here. I'm just trying to get home for Christmas," Diaz said.
Robin Greene and her family just arrived from Indianapolis. Their connection to Paris is on time, so far. But this was not their originally scheduled flight.
"The flights were disappearing on my computer as we were rebooking. Ugh. It was a bit stressful," she said.
Anyone planning to travel by air Friday should be ready. FlightAware reports more than 2,000 flights are already canceled.
Blizzard conditions are expected from the plains and the Midwest to the East Coast, with high winds and plunging temperatures.
Some airlines have offered weather waivers, which allow travelers to change their flights for free.
Train service is also impacted. Amtrak has canceled service on dozens of routes, and Metra is adjusting its schedule for the cold and windy conditions to come.