The Council on Tall Buildings and Urban Habitat is the international organization that determines the criteria that in turn determine the officially accepted heights of buildings.
In 1997 the council announced four categories of height, measured from sidewalk level: (1) height to structural top, (2) height to floor of highest occupied floor, (3) height to top of roof, and (4) height to tip of spire or antenna. Thus, at that time, the record holders were as follows: in category 1, the Petronas Twin Towers, Kuala Lumpur, Malaysia (1,483 feet [452 metres]); in category 2, the Sears Tower (now called Willis Tower), Chicago (1,431 feet [436 metres]); in category 3, the Sears (Willis) Tower (1,450 feet [442 metres]); and in category 4, One World Trade Center, New York City (1,728 feet [526.7 metres]).
In 2003 the Taipei 101 (Taipei Financial Center) building in Taipei, Taiwan, exceeded the records for the first three categories, respectively, with the following heights: 1,667 feet (508 metres); 1,437 feet (438 metres); and 1,470 feet (448 metres). The record in the final category was surpassed in 2000 by the Sears (Willis) Tower after that building’s west antenna was replaced by one that reached 1,730 feet (527.3 metres). (One World Trade Center subsequently was destroyed in the September 11, 2001, terrorist attacks.)
The council amended its criteria in 2009 to specify that height was to be measured “from the level of the lowest, significant, open-air, pedestrian entrance,” instead of from the sidewalk level. The council’s amendment was an allowance for multi-use buildings with various entrances at different levels. In addition, in light of the decline of flat-topped towers in favour of those whose precise “roofs” were growing increasingly difficult to determine, the third category, that measuring the height to the top of the roof, was discarded.
In January 2010 the inauguration of the Burj Khalifa in Dubai, U.A.E., marked new records in all three recognized categories. The new tower measured 2,717 feet (828 metres) at its structural top, reached 2,039 feet (621 metres) at its highest occupied floor, and measured 2,723 feet (830 metres) to the tip of its spire.
Because the September 11 attacks caused such massive destruction and intensely hot fires, the remains of many victims were never recovered, and others remained unidentifiable. Consequently, the precise number of victims—particularly the number of those killed at the World Trade Center—has remained unclear. Flight manifests provided information on the number of passengers and crew on each of the ill-fated airliners, and tight security procedures at the Pentagon gave investigators a clear picture of who was in the building at the time of the attacks. Access to the World Trade Center, however, was not thoroughly documented or tightly monitored, and there was no clear way to determine who exactly was in either of the towers at the time of their collapse. That issue was compounded by the fact that hundreds of those who worked in the towers were foreign nationals—including perhaps some who were undocumented workers—which made exact identification difficult if not impossible. In addition, the generous financial remuneration that the U.S. government offered the families of the deceased motivated some unscrupulous individuals to make fictitious claims that loved ones or family members had been among those killed. On the first anniversary of the attacks, the official toll of those killed in New York (including the passengers and crew of the two aircraft that struck the towers) rested at 2,801, but that number was soon amended when several names were determined to have been erroneous or listed twice. The new death toll of 2,792 remained unchanged until late 2003, when it was lowered to 2,752 after 40 more names were deemed to be either inaccurate or fraudulent. Given the 184 victims killed at the Pentagon and the 40 killed in Pennsylvania, the overall death toll of the September 11 attacks was reckoned at that time to be 2,976 persons. That number was later revised to 2,977. Most estimates of the September 11 death toll, whether official or unofficial, do not include the 19 hijackers in their calculations.
