Celebrating the airport's brand new runway that is not even open to air traffic yet, it was opened up to thousands of runners first for the O'Hare Run on the Runway.
"For me, it's kind of like seeing a baby eating ice cream for the first time," said United Airlines worker Jared Pasparage.
They were excited, to say the least, to race to the airport in a different way.
"Well, I'm looking forward to seeing all the planes and everything," said runner Jillian Locke. "It's different scenery than what I'm used to."
Runners ran on a runway in a normally prohibited area and even United Airlines workers wanted a chance to be up close to their airport.
"I think it's a great experience, not only to represent United, but you know, for my first running experience to be sort of close to what has been a big part of my life for 20 years, and that's the aviation industry, so very excited about it," United worker Cliff Riley said.
The new runway, formally called 10c-28c, will officially open to air traffic on October 17 as part of O'Hare's expansion project.
"We are consistently changing so we can be the most efficient airport we need to add capacity and reduce delays and create the efficiency the traveling public demands," said Rosemarie Andolino, Commissioner of Chicago Department of Aviation.
Proceeds from Sunday's run go towards the Wounded Warrior Project, helping those injured in the armed services.