NEW YORK, NY - MAY 25: People visit the National 9/11 Memorial Museum in New York, United States on May 25, 2014. The National 9/11 Memorial Museum was opened to the public for the first time on May 21, 2014 and telling the story of 9/11 through multimedia displays, archives, narratives and a collection of monumental and authentic artifacts. (Photo by Cem Ozdel/Anadolu Agency/Getty Images)

NEW YORK, NY - MAY 25:  People visit the National 9/11 Memorial Museum in New York, United States on May 25, 2014. The National 9/11 Memorial Museum was opened to the public for the first time on May 21, 2014 and telling the story of 9/11 through multimedia displays, archives, narratives and a collection of monumental and authentic artifacts. (Photo by Cem Ozdel/Anadolu Agency/Getty Images)