News: the owners of an observation deck on the 94th storey of Chicago's John Hancock Center are considering adding a glass box into which visitors would be strapped and tilted forward to experience a bird's eye view of the city below.

According to local business newspaper Crain's Chicago Business, the observatory's owner hopes the attraction, called the Tilt, could compete with the popular glass-floored observation boxes called the Ledge that were added to the 103rd floor of the nearby Willis Tower in 2009.

Paris-based Montparnasse Group 56 bought the John Hancock Observatory in 2012 for $44.2 million and operates it as a separate enterprise from the rest of the spaces inside the 100-storey tower, which was designed by Skidmore, Owings & Merrill and completed in 1969.

"It's no secret that observation decks as a business are very profitable, as opposed to leasing square footage in the building," Daniel Thomas, executive director of the World Federation of Great Towers and a former general manager of the Hancock Observatory told Crain's.

Thomas added that he estimates the John Hancock Observatory currently makes over $10 million annually from tickets that cost $18, while the Willis Tower's income from ticket sales starting at $19 could be as much as $25 million.

Developers of tall buildings are increasingly seeking to add or include observation decks in response to evidence of their popularity and profitability, such as figures released by the owners of New York's Empire State Building during its IPO proceedings. Empire State Realty Trust declared that its rooftop viewing area generates $92 million annually – approximately 40 percent of its total revenue. Adult tickets for the main observation deck on the 86th storey of the Empire State Building cost $27, while a combined ticket for the main deck and the top deck on the 102nd storey is $44.

If the Tilt is approved, it would join other extreme observation experiences such as the thrill rides located at the top of the 350 metre Stratosphere Tower in Las Vegas, a harnessed outdoor walkway on the 61st floor of the Macau Tower in Hong Kong Macau and a similar attraction 356 metres above Toronto at the CN Tower.

Photographs of John Hancock Centre and Willis Tower are courtesy of Shutterstock.