"I fly a lot," one passenger told ABC7 Chicago.
Like others, Des Moines, Iowa native Jean Mountain was moving ahead with her trip to Italy Sunday, although the state department warned U.S. citizens to take personal security precautions while traveling abroad because of heightened concerns about a potential al Qaida attack aimed at Americans and Europeans.
"I'm going from the southern part to the northern part, and my biggest concern is rain spoiling my pictures," Mountain said.
Europeans traveling also seemed equally unfazed.
"Sometimes, it's more wise don't mention it," another man said.
While Sunday's alert is one step below a formal travel warning advising Americans not to visit Europe, city officials Chicago is not a target.
"We have no information that would suggest an elevated threat against the city of Chicago," police Supt. Jody Weis said. "It's all overseas."
For days, U.S. and European security experts have been concerned there may be plots in Europe similar to the deadly 2008 shooting spree in Mumbai, India.
Members of the Arnold family from Woodstock, Ill. returned home from Spain Sunday afternoon and said security was tight at European airports.
"This morning, when you go through the security, I beeped and they did a full pat down, very scary. And later on, they asked to do the kids, too," Diedre Arnold said.
The U.S. travel alert could hurt European tourism and dampen business travel, leading some to call the alert, which doesn't identify specific targets, too vague.
"We're not hearing any specific information about targets, locations, timing, or any really valuable advice to Americans about what they can do," said Frances Townsend, former Homeland Security advisor.
Still, traveler Carol Stone said she saw this recent development as a sign of the times.
"You just have to live your life and not worry about it," said Stone.
That's what it seem a lot of travelers were doing Sunday: simply not worrying about it. There are hundreds of thousands of Americans in Europe either traveling as tourists or attending school there or tending to business, which is the reason the United States government issued the alive.