Context of '9:47 a.m. September 11, 2001: Internal Collapse at WTC South Tower Reported'

Flight 175 hits the WTC South Tower. The picture was taken from a traffic helicopter. [Source: WABC 7/ Salient Stills]Flight 175 hits the South Tower of the World Trade Center (Tower Two). Seismic records pinpoint the time at six seconds before 9:03 a.m. (rounded to 9:03 a.m.). Hijackers Marwan Alshehhi, Fayez Ahmed Banihammad, Mohand Alshehri, Hamza Alghamdi, and Ahmed Alghamdi presumably are killed instantly, and many more in the tower will die over the next few hours. [New York Times, 9/12/2001; CNN, 9/12/2001; CNN, 9/17/2001; North American Aerospace Defense Command, 9/18/2001; USA Today, 12/20/2001; Federal Emergency Management Agency, 5/1/2002, pp. 1-10; New York Times, 5/26/2002; Associated Press, 8/21/2002; USA Today, 9/2/2002] According to the NIST report, the crash time is 9:02:59. [National Institute of Standards and Technology, 9/2005, pp. 38] According to the 9/11 Commission Report, the crash time is 9:03:11. [9/11 Commission, 7/24/2004, pp. 8] Millions watch the crash live on television. The plane strikes the 77th through 85th floors in the 110-story building. Approximately 100 people are killed or injured in the initial impact; 600 people in the tower eventually die. The death toll is far lower than in the North Tower because about two-thirds of the South Tower’s occupants have evacuated the building in the 17 minutes since the first tower was struck. [USA Today, 12/20/2001; National Institute of Standards and Technology, 9/2005, pp. 5-9, 41] The combined death toll from the two towers is estimated at 2,819, not including the hijackers. [Associated Press, 8/21/2002] The impact severs some columns on the south side of the South Tower. Each of the Twin Towers is designed as a “tube-in-tube” structure and the steel columns which support its weight are arranged around the perimeter and in the core. The plane, which is traveling at an estimated speed of around 500 mph (see October 2002-October 2005), severs 33 of the building’s 236 perimeter columns and damages another one. [National Institute of Standards and Technology, 9/2005, pp. 39] The perimeter columns bear about half of the tower’s weight, so the damage to them reduces the tower’s ability to bear gravity loads by about 7.1 percent. [National Institute of Standards and Technology, 9/2005, pp. 6] The actual damage to the 47 core columns is not known, as there are no photographs or videos of it, but there will be much speculation about this after 9/11. It will be suggested that some parts of the aircraft may be able to damage the core even after crashing through the exterior wall (see 8:46 a.m. September 11, 2001). [National Institute of Standards and Technology, 9/2005, pp. 107] According to NIST’s base case model, five of the core columns are severed and another five suffer some damage. [National Institute of Standards & Technology, 9/2005, pp. 235 ] This may reduce the tower’s ability to bear loads by a further approximately 8 percent, meaning that the aircraft impact accounted for a loss of about 15 percent of the building’s strength. This damage will be cited as an event contributing to the building’s collapse after 9/11 (see October 23, 2002 and October 19, 2004). NIST’s base case estimate of damage to the North Tower’s core will be similar, even though the aircraft impact there was dissimilar (see 8:46 a.m. September 11, 2001). Flight 11 hit the North Tower’s core head on, whereas Flight 175 only hits the corner of the South Tower’s core. [National Institute of Standards and Technology, 9/2005, pp. 20-23, 38-41] In addition, some of the fireproofing on the steel columns and trusses may be dislodged (see 8:46 a.m. September 11, 2001). [National Institute of Standards & Technology, 9/2005, pp. xxxvi, 83 ] Photographs and videos of the towers will not show the state of fireproofing inside the buildings, but the National Institute of Standards and Technology (NIST) will try to estimate the damage to fireproofing using a series of computer models. Its severe case model (see (October 2002-October 2005)) will predict that 39 of the 47 core columns are stripped of their fireproofing on one or more floors and that fireproofing is stripped from trusses covering 80,000 ft2 of floor area, the equivalent of about two floors. NIST will say that the loss of fireproofing is a major cause of the collapse (see April 5, 2005), but only performs 15 tests on fireproofing samples (see October 26, 2005). [National Institute of Standards and Technology, 9/2005, pp. 41] According to NIST, less fireproofing is stripped from the North Tower (see 8:46 a.m. September 11, 2001).

A man who is on the 105th floor of the South Tower calls emergency 9-1-1 to report that floors below his location, “in the 90-something floor,” have collapsed. The 9-1-1 operator types a record of this call into the Special Police Radio Inquiry Network (SPRINT) data link, which will be passed on to the New York fire department’s Emergency Medical Service (EMS). It isn’t known when the call is made exactly, but the EMS Dispatch computer apparently receives the call record at this time. However, because it is classified as a “supplement message,” it is not yet read by anyone. The police dispatcher dealing with the area around the WTC also receives the call record, but misinterprets it as meaning that the floor the person is on has collapsed. EMS dispatchers are dealing with an enormous volume of calls as well as performing many other tasks under extreme pressure during the crisis, so a report later concludes that the EMS operators didn’t have the time to review the information before the collapse of the South Tower at 9:59 (see 9:59 a.m. September 11, 2001), and the fire chiefs never received the information. [New York City Fire Department, 8/19/2002]

The South Tower of the World Trade Center collapses. [Source: Associated Press]The South Tower of the World Trade Center tilts to the southeast and then collapses. It was hit by Flight 175 at 9:03 a.m., 56 minutes earlier (see 9:03 a.m. September 11, 2001). [Washington Post, 9/12/2001; New York Times, 9/12/2001; MSNBC, 9/22/2001; USA Today, 12/20/2001; Associated Press, 8/21/2002; ABC News, 9/11/2002; National Institute of Standards and Technology, 9/2005, pp. 44] The first sign of the collapse is visible on floor 82. [National Institute of Standards and Technology, 9/2005, pp. 87] The angle of the tilt will be disputed after 9/11 (see September-November 2005), as will the time it takes the towers to fall to the ground (see September 12, 2001-September 2005). [Scientific American, 10/9/2001; Eagar and Musso, 12/2001; PBS Nova, 5/2002; National Institute of Standards and Technology, 8/30/2006]

Damage to the southwest corner of WTC 7. [Source: Arquelio Galarza]World Trade Center Building 7 (WTC 7) suffers some damage, caused by debris from the collapse of the north WTC tower, according to later official reports. [Federal Emergency Management Agency, 5/1/2002, pp. 5-16; National Institute of Standards and Technology, 11/2008, pp. 16 ]
WTC 7 Undamaged by South Tower Collapse - WTC 7 is a 47-story office building located 370 feet north of the North Tower (WTC 1). In the final report of its investigation into WTC 7’s collapse, published in November 2008 (see November 20, 2008), the National Institute of Standards and Technology (NIST) will state that although a few windows on the lower floors of WTC 7’s south face were broken when the South Tower (WTC 2) collapsed at 9:59 a.m. (see 9:59 a.m. September 11, 2001), “None of the large pieces of debris from WTC 2 hit WTC 7, because of the large distance between the two buildings,” and there is “no evidence of structural damage to WTC 7” as a result of the South Tower’s collapse.
Debris Reportedly Damages Exterior Columns - However, when the North Tower collapses (see 10:28 a.m. September 11, 2001), some fragments of debris are “forcibly ejected” from it, and travel “distances up to hundreds of meters.” According to NIST, pieces of this debris “hit WTC 7, severing six columns on floors 7 through 17 on the south face and one column on the west face near the southwest corner.” NIST will add that the debris also causes “structural damage between floor 44 and the roof,” and breaks a large number of windows on WTC 7’s south face.
Building Core Undamaged - However, NIST will state, based on “photographic evidence, witness accounts, and engineering judgment, it is likely that the structural damage (steel and floor slabs) did not penetrate beyond the perimeter of the building core. At the southwest corner, the structural damage extended only about one-third of the distance from the exterior wall to the building core.” NIST will comment, “Compared to the airplane impact damage to the WTC towers, there was relatively little damage to the interior of WTC 7.” There is also “no superficial or structural damage” to WTC 7’s north and east faces. And the sprayed fire resistive material that has been applied to the building’s steel columns, girders, and beams is only damaged in the “immediate vicinity of the WTC 1 debris impact.” NIST will admit, however, that there are “uncertainties” in its accounting of the events leading up to the collapse of WTC 7, because “the remains of all the WTC buildings were disposed of before Congressional action and funding was available for [its] investigation [of the WTC collapses] to begin” (see Shortly After September 11, 2001 and September 12-October 2001). [National Institute of Standards and Technology, 8/21/2008; National Institute of Standards and Technology, 11/2008, pp. 15-16 ]
FEMA Describes WTC 7 Damage - According to an earlier report on the collapse of WTC 7, published by the Federal Emergency Management Agency (FEMA) in May 2002 (see May 1, 2002), at that time, the “extent and severity of the resulting damage to WTC 7” when the North Tower collapses “are currently unknown.” But based on “photographic evidence and eyewitness accounts,” it is “assumed that the south side of the building was damaged to some degree.” FEMA’s report will state: “It does not appear that the collapse of WTC 1 affected the roof, or the east, west, and north elevations of WTC 7 in any significant way. However, there was damage to the southwest corner of WTC 7 at approximately floors 8 to 20, 24, 25, and 39 to 46.” The report will add: “According to firefighters’ eyewitness accounts from outside of the building, approximately floors 8-18 were damaged to some degree. Other eyewitness accounts relate that there was additional damage to the south elevation.” [Federal Emergency Management Agency, 5/1/2002, pp. 5-16, 5-20]
Structural Damage Not Responsible for Collapse - WTC 7 will collapse at 5:20 p.m. this afternoon (see (5:20 p.m.) September 11, 2001). [National Institute of Standards and Technology, 8/21/2008] However, NIST will conclude that the structural damage the building suffers plays no role in causing it to come down. NIST will state, “Other than initiating the fires in WTC 7, the damage from the debris from WTC 1 had little effect on initiating the collapse of WTC 7.” [National Institute of Standards and Technology, 11/2008, pp. xxxvii ] WTC 7 suffers fires on some floors, which are reportedly initiated by debris from the collapse of the North Tower (see (10:28 a.m.-5:20 p.m.) September 11, 2001). According to NIST, it is these fires, “rather than the structural damage that resulted from the impacts” of debris, which “initiated the building’s collapse.” [National Institute of Standards and Technology, 8/21/2008]

At around 8:00 p.m., Afghanistan time (11:30 a.m., New York time), Taliban leader Mullah Omar allegedly says, “Things have gone much further than expected.” This is according to what the New Yorker will describe as “Afghan intelligence sources” who monitor the call. (It is unclear what “Afghan intelligence sources” means, since the Taliban control nearly all of Afghanistan at this time, but it could be a reference to Northern Alliance forces; the CIA gave them equipment to monitor the Taliban (see Winter 1999-March 2000).) Omar’s comment takes place over an hour after one of the World Trade Center towers collapsed, which means thousands have been killed in the attacks, not hundreds (see 9:59 a.m. September 11, 2001). An Afghan intelligence official will later say: “They were expecting a reaction. But they thought it would be a Clinton-type reaction. They didn’t anticipate the kind of revenge that occurred.” [New Yorker, 6/10/2002] The “Clinton-type reaction” presumably is a reference to the August 1998 missile strikes on Sudan and Afghanistan during the Clinton administration (see August 20, 1998).

Following the attacks, there is no agreement on the speed with which the Twin Towers of the World Trade Center collapsed on 9/11 (see 9:59 a.m. September 11, 2001 and 10:28 a.m. September 11, 2001). The 9/11 Commission says that the South Tower collapsed in “ten seconds” and the National Institute of Standards and Technology says that tops of the buildings came down “essentially in free fall.” [9/11 Commission, 7/24/2004, pp. 305; National Institute of Standards and Technology, 9/2005, pp. 146] In the dispute over the reason for the WTC’s collapse after 9/11, it is claimed that, if the towers fell in ten seconds, then this is evidence they were destroyed by explosives. For example, David Ray Griffin, a theologian and outspoken critic of commission’s report, writes, “For a 1,300-foot building, however, ten seconds is almost free-fall speed. But if each floor produced just a little resistance, so that breaking through each one took half a second, the collapse of all those floors—80 or 95 of them—would have taken 40 to 47 seconds. Can we really believe that the upper part of the buildings encountered virtually no resistance from the lower part?” [Griffin, 2004, pp. 16] But according to Canadian scientist Frank Greening, who studies the Twin Towers’ collapse, the freefall time would be about 9.6 seconds, and he calculates that it takes longer for the buildings to fall—twelve to thirteen and a half seconds—and states this does not indicate that explosives were used. [Canadian Broadcasting Corporation, 8/25/2005]

Both towers of the World Trade Center tilted to one side before beginning to fall on 9/11 (see 9:59 a.m. September 11, 2001 and 10:28 a.m. September 11, 2001). The National Institute of Standards and Technology, which investigated the collapses (see August 21, 2002), states that the South Tower, which was hit on its south side, tilted about 7-8 degrees to the east and 3-4 degrees to the south, and the North Tower, which was hit on its north side, tilted about 8 degrees to the south, before starting to fall. [National Institute of Standards and Technology, 9/2005, pp. 300, 308 ] However, these findings are criticized by Canadian scientist Frank Greening. After examining photo and video evidence, Greening says that the South Tower tilted by no more than two degrees and the North Tower by no more than three degrees before collapse initiation. Greening also says that the tilt angles NIST gives cannot correspond to the downward movement of the towers’ walls NIST claims before they started to fall, and points out that the tilt angles NIST uses are inconsistent throughout its reports. Though Greening agrees with NIST that the towers were destroyed by the plane impacts and fire damage, he concludes that its computer model is “highly inaccurate and therefore of no value in explaining the demise of the Twin Towers.” [Greening, 11/2005 ] Greening is a leading figure in the post-9/11 dispute over why the WTC collapsed and publishes a series of papers dealing with various aspects of the Twin Towers’ collapse. For example, a CBC documentary uses Greening for analysis of the WTC’s fall. [Canadian Broadcasting Corporation, 8/25/2005]