<P> In February 2009, the owners announced they were considering a plan to paint the structure silver; this plan was later dropped . The paint would have "rebranded" the building and highlighted its advances in energy efficiency . The estimated cost was $50 million . </P> <P> Since 2007, the building owners have been considering building a hotel on the north side of Jackson, between Wacker and Franklin, at the plaza that is the entrance to the tower's observation deck . The tower's parking garage is beneath the plaza . Building owners say the second building was considered in the original design . The plan was eventually cancelled as city zoning does not permit construction of such a tall tower there . </P> <P> Although Sears' naming rights expired in 2003, the building continued to be called the Sears Tower for several years . In March 2009, London - based insurance broker Willis Group Holdings agreed to lease a portion of the building, and obtained the building's naming rights . On July 16, 2009, the building was officially renamed Willis Tower . On August 13, 2012, United Airlines announced it would move its corporate headquarters from 77 West Wacker Drive to Willis Tower . </P> <P> In 2015, the Blackstone Group completed purchase of the tower for a reported $1.3 billion, the highest price ever paid for a U.S. property outside New York City . The new owners are considering several plans for further site developments . </P>

When did the sears tower became the willis tower