In the first week of September 2001, the real estate development and investment firm Silverstein Properties assumes control of the World Trade Center. The company had acquired the lease to operate the Twin Towers from the New York Port Authority in late July (see July 24, 2001). It has already begun managing the facility with its own executives. Selected Port Authority employees, including Alan Reiss, the director of the World Trade Center, have been assisting the firm during a three-month transition period. But in the weeks prior to 9/11, according to the New York Times, “Silverstein Properties asked Mr. Reiss to let it more fully operate everything from safety systems to tenant relations.” [New York Times, 9/13/2001; New York Times, 10/14/2001; Weiss, 2003, pp. 338; 9/11 Commission, 11/3/2003; 9/11 Commission, 5/18/2004 
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Between September 3, 2001 and September 7, 2001: WTC Structural Engineer Says Trade Center Designed for 707 Crashing Into It
Leslie Robertson, one of the two original structural engineers for the World Trade Center, is asked at a conference in Frankfurt, Germany what he had done to protect the Twin Towers from terrorist attacks. He replies, “I designed it for a 707 to smash into it,” though does not elaborate further. [Chicago Tribune, 9/12/2001; Knight Ridder, 9/12/2001] The Twin Towers were in fact the first structures outside the military and nuclear industries designed to resist the impact of a jet airplane. [Robertson, 3/2002; Federal Emergency Management Agency, 5/1/2002, pp. 1-17] The Boeing 707 was the largest in use when the towers were designed. Robertson conducted a study in late 1964, to calculate the effect of a 707 weighing 263,000 pounds and traveling at 180 mph crashing into one of the towers. He concluded that the tower would remain standing. However, no official report of his study has ever surfaced publicly. [Glanz and Lipton, 2004, pp. 138-139, 366] A previous analysis, carried out early in 1964, calculated that the towers would handle the impact of a 707 traveling at 600 mph without collapsing (see February 27, 1993). In 2002, though, Robertson will write, “To the best of our knowledge, little was known about the effects of a fire from such an aircraft, and no designs were prepared for that circumstance.” [Robertson, 3/2002] The planes that hit the WTC on 9/11 are 767s, which are almost 20 percent heavier than 707s. [Scientific American, 10/9/2001; New Yorker, 11/19/2001]
September 7, 2001: New Security Director Criticizes Poor Security at the World Trade Center
Former FBI counterterrorism chief John O’Neill recently started his new job as director of security at the World Trade Center (see August 23, 2001). From the outset, he has engrossed himself in discovering what security systems are in place there, and what will be needed in future. On this day, he runs into Rodney Leibowitz, a friend of his, and complains to him about the very poor standard of security at the Twin Towers. For instance, he mentions that, even though the complex receives bomb threats on a daily basis, its telephone system does not feature caller identification. [Weiss, 2003, pp. 354 and 358] The Trade Center has in fact recently been on a heightened security alert, due to numerous phone threats (see Late August-September 10, 2001). [Newsday, 9/12/2001] Leibowitz is the president and CEO of a company called First Responder Inc., which provides bioterrorism preparedness training to healthcare professionals. [First Responder Inc., 1/14/2004 ] Until the 9/11 attacks intervene, First Responder Inc. is in fact scheduled to send in a team to conduct a threat assessment of the World Trade Center for O’Neill on September 15. [Swanson, 2003, pp. 52]
September 10, 2001: Anti-Terrorism Meeting at WTC on 9/11 Is Canceled
Silverstein Properties, Larry Silverstein’s company which took over the lease of the WTC weeks earlier (see July 24, 2001), has a meeting planned for the morning of 9/11 in it’s temporary offices on the 88th floor of the WTC North Tower, along with Port Authority officials. It is to discuss what to do in the event of a terrorist attack. However, this evening the meeting is canceled because one participant cannot attend. [New York Times, 9/12/2001; Ha’aretz, 11/21/2001] Of Silverstein Properties’ 160 staff, 54 are in the North Tower when it is hit, and four of them die. [Globe and Mail, 9/7/2002]
8:46 a.m. September 11, 2001: Flight 11 Hits the North Tower of the World Trade Center
Flight 11 slams into the WTC North Tower (Building 1). Hijackers Mohamed Atta Waleed Alshehri, Wail Alshehri, Abdulaziz Alomari, and Satam Al Suqami presumably are killed instantly, and many more in the tower will die over the next few hours. Seismic records pinpoint the crash at 26 seconds after 8:46 a.m. [CNN, 9/12/2001; New York Times, 9/12/2001; 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; USA Today, 8/12/2002; Associated Press, 8/21/2002; Newsday, 9/10/2002] The NIST report states the crash time to be 8:46:30. [National Institute of Standards and Technology, 9/2005, pp. 19] The 9/11 Commission Report states the crash time to be 8:46:40. [9/11 Commission, 7/24/2004, pp. 7] Investigators believe the plane still has about 10,000 gallons of fuel (see 8:57 a.m. September 11, 2001). [New York Times, 5/26/2002] The plane strikes the 93rd through 99th floors in the 110-story building. No one above the crash line survives; approximately 1,360 people die. Below the crash line, approximately 72 die and more than 4,000 survive. Both towers are slightly less than half full at the time of the attack, with between 5,000 to 7,000 people in each tower. This number is lower than expected. Many office workers have not yet shown up to work, and tourists to the observation deck opening at 9:30 A.M. have yet to arrive. [USA Today, 12/20/2001; National Institute of Standards and Technology, 9/2005, pp. 20-22] The impact severs some columns on the north side of the North Tower. Each tower 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 weighs 283,600 lb and is traveling at an estimated speed of around 430 mph (see October 2002-October 2005), severs 35 of the building’s 236 perimeter columns and damages another two. The damage to the South Tower’s perimeter will be similar (see 9:03 a.m. September 11, 2001). [National Institute of Standards and Technology, 9/2005, pp. 5-9, 20, 22] The perimeter columns bear about half of the tower’s weight, so this damage reduces its ability to bear gravity loads by about 7.5 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 have damaged the core even after crashing through the exterior wall. According to the National Institute of Standards and Technology (NIST): “Moving at 500 mph, an engine broke any exterior column it hit. If the engine missed the floor slab, the majority of the engine core remained intact and had enough residual momentum to sever a core column upon direct impact.” [National Institute of Standards and Technology, 9/2005, pp. 107] According to NIST’s base case computer model, three of the core columns are severed and another ten suffer some damage. [National Institute of Standards & Technology, 9/2005, pp. 189 ] If this is accurate, it means that the impact damage to the core reduces the Tower’s strength by another approximately 7.5 percent, meaning that the building loses about 15 percent of its strength in total. This damage will be cited after 9/11 by NIST and others researchers as an event contributing to the building’s collapse (see October 23, 2002 and October 19, 2004). In addition, some of the fireproofing on the steel columns and trusses may be dislodged. The original fireproofing on the fire floors was mostly Blazeshield DC/F, but some of the fireproofing on the flooring has recently been upgraded to Blazeshield II, which is about 20 percent denser and 20 percent more adhesive. [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 NIST will estimate the damage to it using a computer model. Its severe case model (see (October 2002-October 2005)) will predict that 43 of the 47 core columns are stripped of their fireproofing on one or more floors and that fireproofing is stripped from trusses covering 60,000 ft2 of floor area, the equivalent of about one and a half 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. 23] According to NIST, more fireproofing is stripped from the South Tower (see 9:03 a.m. September 11, 2001).
8:47 a.m.-9:50 a.m. September 11, 2001: Engineer Finds Major Damage in Basement and Lobby of North Tower
Mike Pecoraro, an engineer who is part of the crew that services the World Trade Center complex, is at work in the mechanical shop in the second subbasement of the north WTC tower when it is hit. When the room he is in starts filling with white smoke and he can smell kerosene (jet fuel), he heads upstairs with a co-worker toward a small machine shop on the C level. Yet, he will later recall: “There was nothing there but rubble. We’re talking about a 50 ton hydraulic press—gone!” He then heads for the parking garage, yet finds that “there were no walls, there was rubble on the floor, and you can’t see anything.” He ascends to the B level where he sees a 300-pound steel and concrete fire door, which is lying on the floor, wrinkled up “like a piece of aluminum foil.” Pecoraro recalls seeing similar things at the WTC when it was bombed in 1993 and is therefore convinced that a bomb has gone off this time. When he makes it into the main lobby, he sees massive damage. “The whole lobby was soot and black, elevator doors were missing,” he will describe. “The marble was missing off some of the walls. Twenty-foot section of marble, 20 by 10 foot sections of marble, gone from the walls.… Broken glass everywhere, the revolving doors were all broken and their glass was gone.” Pecoraro will say he only later hears that “jet fuel actually came down the elevator shaft, blew off all the [elevator] doors, and flames rolled through the lobby. That explained all the burnt people and why everything was sooted in the lobby.” He makes it out of the North Tower before it collapses. [Chief Engineer, 8/1/2002]
8:57 a.m. September 11, 2001: Jet Fuel in North Tower Burns Up
The jet fuel that spilled from Flight 11 when it hit the North Tower (see 8:46 a.m. September 11, 2001) has mostly burned up by this time. The National Institute of Standards and Technology (NIST), which investigates the collapses, will say “The initial jet fuel fires themselves lasted at most a few minutes.” [National Institute of Standards and Technology, 9/2005, pp. 183] Engineering professor Forman Williams will say the jet fuel “burned for maybe 10 minutes.” [Popular Mechanics, 3/2005] Flight 11, a Boeing 767, had a fuel capacity of 23,980 gallons, but was only carrying about 10,000 gallons when it hit the WTC. NIST will estimate that less than 1,500 gallons were consumed in a fireball inside the tower and a comparable amount was consumed in the fireballs outside the building. Therefore, approximately 7,000 gallons splashed onto the office furnishings and started fires on various floors. However, after the jet fuel is used up, office fires burn until the building collapses. NIST will calculate that there were about four pounds per square foot of combustibles in the office space, or about 60 tons per floor. Offices in the WTC actually have fewer combustibles than some other similar spaces due to the small number of interior walls and limited bookshelf space. NIST will later find that only three of sixteen perimeter columns it recovers reached a temperature of 250°C and neither of the two core columns it retrieves reached this temperature. NIST will also find that none of the samples it acquires reaches a temperature above 600°C (see August 27, 2003). Although steel does not melt until its temperature is about 1,600°C, it may begin to lose significant strength at over 500°C. [National Institute of Standards and Technology, 9/2005, pp. 20, 29, 24, 77] The jet fuel will also burn up in the South Tower about 10 minutes after it is hit (see 9:13 a.m. September 11, 2001).
9:03 a.m. September 11, 2001: Flight 175 Crashes into WTC South Tower; Millions Watch Live on Television
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).
Between 9:10 a.m. and 9:15 a.m. September 11, 2001: South Tower Employee Sees No Inferno on 78th Floor
Brian Clark, the executive vice president of brokerage firm Euro Brokers, was on the 84th floor of the South Tower, where his firm’s offices are, when Flight 175 crashed into it. He had headed out, going down Stairway A, which is the only staircase in the tower that remains intact from top to bottom, and was soon joined by Stanley Praimnath, who also works in the South Tower. They reach a point that Clark later guesses to have been around the 77th or 78th floor, where the stairway walls are cracked, allowing them to look through. This would be around the lower end of the floors where the plane impacted. However, Clark sees no large fire. He later says, “[Y]ou could look through the cracks and see flames. They were just quietly licking up, not a roaring inferno. And there was some smoke there, but again I think the stairs were pressurized, pushing the air out so we had less smoke in the stairway than you might imagine.” [BBC, 3/7/2002; New York Times, 5/26/2002; Sun, 9/6/2002; 9/11 Commission, 5/18/2004] This apparently contradicts later claims that the tower was subjected to “extreme fires” prior to its collapse. [New York Times, 10/20/2004] Firefighter Orio Palmer will make it up to this level of the tower later on, and also report only finding small fires there (see 9:52 a.m. September 11, 2001). Clark and Praimnath continue down the stairs and make it out just minutes before the collapse. They are two of only four people who were at or above the impact zone after Flight 175 hit, who are able to escape from the South Tower. [CNN, 9/9/2002] A further 14 people are able to get out of the building from its 78th floor, which is the lower part of the crash zone. [Dwyer and Flynn, 2005, pp. 255]
9:13 a.m. September 11, 2001: Jet Fuel in South Tower Burns Up
The jet fuel that spilled from Flight 175 when it hit the South Tower (see 9:03 a.m. September 11, 2001) has mostly burned up by this time. The National Institute of Standards and Technology (NIST), which later investigates the collapses, will say the “initial jet fuel fires themselves lasted at most a few minutes.” [National Institute of Standards and Technology, 9/2005, pp. 183] Engineering professor Forman Williams will say the jet fuel “burned for maybe 10 minutes.” [Popular Mechanics, 3/2005] Flight 175, a Boeing 767, had a capacity of 23,980 gallons, but was only carrying about 9,100 gallons of fuel when it hit the WTC. NIST will estimate that less than 1,500 gallons were consumed in a fireball inside the tower and 910 to 2,275 gallons were consumed in the fireballs outside the building. Approximately 6,100 gallons therefore splashed onto the office furnishings and started fires on various floors. However, after the jet fuel is used up, office fires burn until the building collapses. NIST will calculate that there were about four pounds per square foot of combustibles in the office space, or about 60 tons per floor. Offices in the WTC actually had fewer combustibles than other similar spaces due to the small number of interior walls and limited bookshelf space. NIST will later find that only three of sixteen perimeter columns it recovers reached a temperature of 250°C and neither of the two core columns it retrieves reached this temperature. NIST will also find that none of the samples it acquires reached a temperature above 600°C (see August 27, 2003). While steel does not melt until its temperature is about 1,600°C, it may begin to lose significant strength at over 500°C. [National Institute of Standards and Technology, 9/2005, pp. 29, 38, 42, 77] The jet fuel also burned up in the North Tower about 10 minutes after it was hit (see 8:57 a.m. September 11, 2001). When a group of firefighters reach the bottom impact floor in the South Tower just before collapse, they only find two isolated fires (see 9:52 a.m. September 11, 2001).
