Crews worked to repair a box of The Ledge, the 103rd floor tourist attraction atop Chicago’s Willis Tower, after cracks appeared underneath a group of tourists in what an official said was a coating designed to prevent scratches on the glass.
Several workers could be seen carrying a quarter-inch think protective glass Thursday afternoon, which was designed to go over the box’s 1.5-inch thick structural glass.
Officials said the protective layer is replaced every 5-8 months and has cracked three times in the last 5 years.
Alejandro Garibay, his brother, and two cousins were in the glass enclosure that juts out of the west side of the building shortly before 10 p.m. Wednesday when Garibay said they heard cracking.
"Crazy feeling and experience," Garibay wrote in an email to NBC Chicago.
Brian Rehme, a spokesman for public relations firm FleishmanHillard, insisted the structural integrity of The Ledge boxes were sound.
Officials said the structural glass is designed to hold up to 10,000 pounds and believe someone may have dropped something on the protective layer, causing the crack.
Still, it was a frightening experience for the family members visiting from California. Garibay said he and others were joking with staff about the strength of the boxes even before his group walked out into one of the boxes.
"They jokingly and confidently responded, 'It's unbreakable,' so we just went on," said Garibay.
While he and his family members were on the Ledge, Garibay said he heard cracking. They stepped off and alerted staffers.
"I walked them over so they could see and they were totally shocked and asked us to step away and then proceeded to start calling staff and techs and I don't know who else. When we pulled our phones to start recording and take pictures they asked us to leave right away," he said.
Rehme said the visitors were never in any danger.
"This coating does not affect the structural integrity of The Ledge in any way. Occasionally, the coating will crack, as it is designed to in order to protect the surface of the glass," Rehme said in a statement.
The box is expected to reopen Friday, officials said.