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The USO of Illinois organized the performance on Thursday to honor our country's veterans.
The airport posted a video of the full performance on social media that has been watched 45,000 times since it was published Thursday.
The performance began with a lone cadet singing in the rotunda of terminal 3. More young men and women began to filter in around him, joining in on the fun.
The world-renowned singers eventually moved onto a dual staircase where they finished the performance with "God Bless America."
Constance Chase, the director of the glee club, told ABC News that getting on the road with the cadets and doing something outside their normal structure quickly became one of her favorite memories to date since she joined the group in 1999.
“It’s very rare that the cadets have an opportunity to be spontaneous, so that makes it really fun,” Chase said.
They didn’t rehearse in the airport beforehand so they scouted the area in small groups prior to the performance.
“We were all looking at our watches and when they heard the music start all of the cadets found a time to sneak in,” Chase explained. “It’s just fun to do something so off the cuff.”
The group will perform throughout the city of Chicago at various locations leading up to the city’s Veterans Day event at Soldier Field on Saturday.