The storms caused major problems at Chicago-area airports, especially at O'Hare, where at least 325 flights were canceled.
Many stranded passengers were saying Monday that it had been a very long night as they tried to get out of O'Hare. A lot of them actually spent the night at the airport.
Security lines, however, were moving faster Monday.
On Sunday night, delays accompanied the cancelations and caused a backlog of Terminal 1 travelers who were trying to find out if there was any way they could get to their destinations. Some passengers said they spent more than 12 hours at O'Hare -- only to have their flights cancelled because of the thunderstorms.
Obviously, that led to some serious frustration.
"Six hours or so standing in line," passenger Harry Thompson said. "And nobody has been helpful, nobody. No accommodations."
Many passengers said they felt the weather was only a small part of the problem. Long lines had travelers upset. Some say they were given vouchers only to find out they could not get back to their hotel, and people had troubles getting their luggage.
"It really is outrageous. I've never met ruder people in my life!" said Phil Brooks. "I have been in line down here probably five hours. It's just frustrating."
A lot of passengers were complaining about United Airlines and how they say it handled the cancelations and delays.
Carin Yablonski was one of many passengers who had to spend the night at the airport.
"There were no hotel rooms. They offered no food, nothing. Had they told people -- we wanted our luggage back -- we would rent a car. They would not even return our luggage," Yablonski said.
Yablonski was still waiting for a new flight Monday. She says she could have driven back to Pennsylvania by now if she'd had her bags. She says the delay will cause her to lose a week's worth of pay.
"United really screwed up. I mean, it was a horrible experience," she said.
A United spokesperson said Monday morning that the airline was working hard to accommodate its customers in a timely manner.
Meanwhile, other airlines also had to play catch up Monday to get stranded passengers rebooked on new flights.
"[It was] tiresome. [I'm] a bit angry, but I guess we'll have to do Chicago today. So, I guess we will have breakfast and take the Blue track into the city," Marlene Kvarmhaell.
"We've been trying to sleep, which is difficult. Hopefully, [we will] check the baggage in and have a walk around or something," Italico Girolami said.
There were also reports of one plane at O'Hare being stuck on the tarmac for more than two hours because it could not get a gate assignment. ABC7 Chicago has asked the Dept. of Aviation to look into that.
The Dept. of Aviation website listed at least 16 additional cancelations at O'Hare Monday.
Some travelers at Midway Airport were frustrated, as well. Passengers reportedly experienced delays of approximately 30 minutes.