A protective coating on a glass sightseeing box that extends from the 103rd floor of the Willis Tower in Chicago cracked Wednesday night, but officials said no one was ever in danger.

Tourist Alejandro Garibay and four of his family members were standing in one of the glass boxes that jut out from the side of the tower when they heard a strange, worrisome noise below them.

A Willis Tower spokesman Bill Utter clarified Thursday that it was a protective coating, not glass, that cracked -- as it sometimes does.

"At no time whatsoever was the integrity of the structure compromised," he said.

The ledges are designed to hold 5 tons, and the coating keeps the glass from being scratched.

"The protective layer did exactly what it was supposed to do," Utter said.

The four Skydeck ledges are a series of clear bays with glass floors that extend a little more than 4 feet from the building. Visitors can see the street 1,353 feet below their feet. According to the Skydeck website, each bay is made from three layers of half-inch thick glass.

Visitors who step into one of the boxes can see for 50 miles across four states.
Since 2009, 6 million people have ventured into the ledges, which retract into the tower when the windows need cleaning.

The ledges were closed for some time Thursday, but the Skydeck viewing area on the 103rd floor was open.

Around 7 p.m., Willis Tower's Facebook page indicated that "the new protective coating on Ledge 4 has been installed."

"Skydeck Chicago is open, including the other three unaffected Ledges, and Ledge 4 will be back open tomorrow," the post added alongside photos of workers at the scene.

The Hancock Building nearby has a new glass observation feature, but visitors hold on to handrails as the section tilts out about 1,000 feet above the city streets.

【新闻快讯】

位于美国芝加哥的威利斯大厦是全美第二高楼(世界第八)。在大厦的顶层有四个观景室，地板是用透明玻璃构成的，可以从里面对芝加哥进行全方位的观景。然而29日，其中一个观景室的地面玻璃开裂，让当时站在上面的游客惊出一身冷汗。

当时，阿莱扬德罗跟其他三个亲戚正在参观芝加哥的这座摩天大楼并坐在观景台拍照，突然间，他们屁股下面的玻璃开裂了，发出了一阵阵破裂的声音。要知道，他们当时可是在400多米的高度，万一玻璃全碎了，后果不堪设想。

“我的手放在了地面上，我能感受到它正在开裂。”阿莱扬德罗说，“说实话，我真是吓坏了。”讽刺的是，游客在走上玻璃观景台之前，工作人员会告知他们地面的玻璃可以承受5吨的重量，是牢不可破的。

第二天早晨，楼上的四个观光台都被关闭进行例行检查，并更换了破损的部分。

该大楼发言人表示，破裂只是玻璃的表层，玻璃本身仍安全。发言人也说，这破碎情况不寻常，但以前曾发生过。

据报道，威利斯大厦楼高442.3米，共地上108层，地下3层，1974年落成，当时还是全球最高大楼。

威利斯大厦在2009年新增观景台，它于103楼外墙增加四个玻璃观景室，全以强化玻璃打造，可让民众踏出楼外约1.3米。

而此次玻璃碎裂事件正是这凌空于几百米高空的观景台地板玻璃碎裂，真是让人心惊胆颤啊。