Flight 175 passes from the airspace of the FAA’s Boston Center to the airspace of the New York Center, which is in Ronkonkoma, New York. [9/11 Commission, 8/26/2004, pp. 20] New York Center air traffic controller Dave Bottiglia takes over monitoring the flight from Boston Center controller John Hartling (see (8:34 a.m.) September 11, 2001). Flight 175 waits nearly 45 seconds to check in with Bottiglia. According to author Lynn Spencer, this is “rather long, and Bottiglia is just about to call the plane.” But then Captain Victor Saracini, the pilot of Flight 175, makes radio contact, saying, “New York, United 175 heavy.” [Gregor, 12/21/2001 
; Spencer, 2008, pp. 36]
Between 8:40 a.m. and 8:54 a.m. September 11, 2001: Boston Center Military Liaison Calls New York Center with Report about Flight 11; Timing Unclear
Colin Scoggins, the military liaison at the FAA’s Boston Center, calls the FAA’s New York Center but is quickly cut off when the air traffic controller who answers says the center is busy dealing with a hijacking. According to author Lynn Spencer, Scoggins “calls New York Center to notify them that American 11 appears to be descending toward New York, most likely to land at JFK” International Airport. But the controller who takes the call snaps at him: “We’re too busy to talk. We’re working a hijack,” and then hangs up. According to Spencer, the New York Center controller is referring to Flight 175, but “Scoggins just figures that he’s talking about American 11. He has no idea that a second airliner is in crisis.” However, the timing of this call is unclear. If it is made while Flight 11 is descending toward New York, this would mean it occurs in the minutes before 8:46, when Flight 11 crashes (see 8:46 a.m. September 11, 2001). But in Spencer’s account, the call is made just after New York Center controller Dave Bottiglia notices that Flight 175’s transponder code has changed and he calls out to another controller, “I can’t get a hold of UAL 175 at all right now and I don’t know where he went to” (see 8:51 a.m.-8:53 a.m. September 11, 2001). [Spencer, 2008, pp. 48-49] The transcript of radio communications between the New York Center and Flight 175 shows that this would mean Scoggins’s call occurs around 8:53 a.m.-8:54 a.m., about seven minutes after Flight 11 crashes. [New York Times, 10/16/2001]
8:41 a.m.-8:42 a.m. September 11, 2001: Flight 175 Reports ‘Suspicious Transmission’ Heard over Radio as It Departed Airport
Just after Flight 175 enters the airspace of the FAA’s New York Center (see 8:40 a.m. September 11, 2001), its pilot reports to the air traffic controller now managing the flight a suspicious transmission he had heard on departing Boston’s Logan Airport. The pilot, Captain Victor Saracini, tells the controller, Dave Bottiglia: “We figured we’d wait to go to your center. Ah, we heard a suspicious transmission on our departure out of Boston, ah, with someone, ah, it sounded like someone keyed the mikes and said, ah, ‘Everyone, ah, stay in your seats.’” [New York Times, 10/16/2001; 9/11 Commission, 7/24/2004, pp. 21; Spencer, 2008, pp. 36] Saracini is presumably referring to one of the three radio transmissions from Flight 11, where the voice of a hijacker could be heard (see 8:24 a.m. September 11, 2001 and (8:34 a.m.) September 11, 2001). However, none of these had included the hijacker telling people to stay in their seats, as Saracini describes, although the second and third transmissions included the hijacker telling the passengers, “Nobody move.” [9/11 Commission, 7/24/2004, pp. 19] Bottiglia responds: “Oh, okay. I’ll pass that along.” Referring to the fact that this was the end of the transmission he heard, Saracini adds, “It cut out,” and then asks Bottiglia, “Did you copy that?” [Gregor, 12/21/2001 ; Spencer, 2008, pp. 36-37] This is the last radio transmission from Flight 175. The 9/11 Commission will conclude that the plane is hijacked within the next four minutes (see (Between 8:42 a.m. and 8:46 a.m.) September 11, 2001). [9/11 Commission, 8/26/2004, pp. 20] According to author Lynn Spencer, since controllers are only given information on a need-to-know basis, Bottiglia was unaware there were problems with Flight 11, which has not yet entered his airspace. He touches his computer screen to connect to the hotline for his sector controller, and then reports: “UAL 175 just came on my frequency and he said he heard a suspicious transmission when they were leaving Boston. ‘Everybody stay in your seats’—that’s what he heard… just to let you know.” [New York Times, 10/16/2001; Spencer, 2008, pp. 36-37]
After 8:41 a.m. September 11, 2001: Air Traffic Control, Unusually, Does Not Contact United Airlines about Communications with Flight 175
Senior United Airlines personnel are, unusually, not informed about air traffic control communications with Flight 175. At 8:41 a.m., the pilots of Flight 175 reported to air traffic controllers that they heard “a suspicious transmission” from another aircraft during their departure out of Boston (see 8:41 a.m.-8:42 a.m. September 11, 2001). Yet the details of this communication with Flight 175 are not passed on to personnel at the United Airlines System Operations Control (SOC) center, just outside Chicago. [9/11 Commission, 8/26/2004, pp. 20]
Manager Receives ‘No Relevant Information about the Hijackings’ – Rich Miles, the manager on duty at the SOC, will later tell the 9/11 Commission that “[w]hile his experience and expectation was that [FAA air traffic control] would communicate to him and to the SOC about ‘strange’ or unusual communications from the cockpit… he could not recall any such communications on 9/11.” He will say that although, “typically, he would receive relevant information from the [air traffic control] system,” he receives “no relevant information about the hijackings” on this day. [9/11 Commission, 11/21/2003 ]
Other Airline Personnel Unaware of Flight 175 Communications – None of the other senior United Airlines officials on duty at the SOC are told about the 8:41 a.m. report made by the pilots of Flight 175. [9/11 Commission, 8/26/2004, pp. 20] These officials will tell the 9/11 Commission that “the dispatchers and managers at the SOC” are in fact “not aware of any communications” between FAA controllers and Flight 175 this morning. [9/11 Commission, 11/20/2003 ] The 9/11 Commission will describe, “SOC personnel at United that we talked to had no idea of the extent of interaction of the [Flight 175] crew with the saga of [Flight 11].” The Commission will add, “We walked down a list of indicators,” but state, “Until we mentioned them, no one we talked to [at United Airlines] was aware of those occurrences.” [9/11 Commission, 11/17/2003 ]
Controllers Communicate with Pilots, Not Dispatchers – The United Airlines officials will say, however, that, “first and foremost,” FAA controllers “communicated directly with airline pilots, not the dispatchers” at the airline. [9/11 Commission, 11/20/2003 ] Ed Ballinger, the United Airlines dispatcher responsible for Flight 175, will comment that “he did not feel that [air traffic control] was under any obligation to share such information [as the details of the 8:41 a.m. communication] with him, because it didn’t apparently affect the safety of any of his flights.” [9/11 Commission, 4/14/2003 ]
Airline Not Advised to Notify Other Planes about Hijackings – The United Airlines officials who talk with the 9/11 Commission will also recall that “they never received any communication… from the FAA or the air traffic control system advising United to contact its aircraft about the hijackings.” The 9/11 Commission will not offer any explanation for the lack of communication between air traffic control and United Airlines. [9/11 Commission, 8/26/2004, pp. 20]
Between 8:42 a.m. and 8:46 a.m. September 11, 2001: Hijackers Take Over Flight 175
According to the 9/11 Commission, Flight 175 is hijacked some time between 8:42—when its flight crew make their last communication with the ground—and 8:46. The Commission describes that the hijackers “used knives (as reported by two passengers and a flight attendant), Mace (reported by one passenger), and the threat of a bomb (reported by the same passenger). They stabbed members of the flight crew (reported by a flight attendant and one passenger). Both pilots had been killed (reported by one flight attendant).” These witness accounts come from phone calls made from the rear of the plane, from passengers who’d been assigned seats in the front or middle of the cabin. According to the Commission, this is “a sign that passengers and perhaps crew [are] moved to the back of the aircraft.” [9/11 Commission, 7/24/2004, pp. 7; 9/11 Commission, 8/26/2004, pp. 20] An employee at the FAA’s Boston Center later says the hijacking occurs when Flight 175 is above Albany, NY, about 140 miles north of New York City. [Telegraph (Nashua), 9/12/2001; Associated Press, 9/13/2001] The first “operational evidence” that something is wrong is at 8:47, when Flight 175’s transponder code changes twice within a minute (see 8:46 a.m.-8:47 a.m. September 11, 2001). [9/11 Commission, 7/24/2004, pp. 7]
8:42 a.m.-8:46 a.m. September 11, 2001: New York Center Controller Informed Flight 11 Is Suspected Hijack, Then Follows It on Radar
After Flight 11 appears on his radar screen, Dave Bottiglia, an air traffic controller at the FAA’s New York Center, is informed that this aircraft is suspected of having been hijacked. Flight 175 entered Bottiglia’s airspace not long before this (see 8:40 a.m. September 11, 2001). [MSNBC, 9/11/2002; 9/11 Commission, 8/26/2004, pp. 20] Its pilot has just told Bottiglia about the “suspicious transmission” (presumably from Flight 11) he heard while departing Boston airport (see 8:41 a.m.-8:42 a.m. September 11, 2001). [Gregor, 12/21/2001 ] Seconds later, Flight 11 also enters the area Bottiglia is monitoring and its target appears on his radar screen. The controller sitting next to Bottiglia gets up and points to the radar blip. He says: “You see this target here? This is American 11. Boston Center thinks it’s a hijack.” Bottiglia will later recall that his initial thought about Flight 11, based on this information, is that the hijackers “were probably going to Cuba.” As its transponder has been turned off (see (Between 8:13 a.m. and 8:21 a.m.) September 11, 2001), he has no altitude information for Flight 11, but can tell from the radar scope that it appears to be descending. According to author Lynn Spencer: “Even without a transponder, controller radars calculate ground speed for all radar targets, and when a plane is descending, the ground speed decreases. The flight had been ‘grounding’ 600 knots, and now it has decreased to 320.” Bottiglia follows Flight 11’s target on his radar screen until it disappears over New York City. [MSNBC, 9/11/2002; Spencer, 2008, pp. 37] Because he is focused on Flight 11, Bottiglia will not notice when Flight 175’s transponder code changes at 8:47 (see 8:46 a.m.-8:47 a.m. September 11, 2001). [9/11 Commission, 7/24/2004, pp. 21; 9/11 Commission, 8/26/2004, pp. 21] The New York Center was first notified of Flight 11’s hijacking at 8:25 a.m. (see 8:25 a.m. September 11, 2001), though this information was not passed on to Bottiglia. [Federal Aviation Administration, 9/17/2001 ; Spencer, 2008, pp. 36-37]
8:43 a.m. September 11, 2001: NORAD Reportedly Notified that Flight 175 Has Been Hijacked, 9/11 Commission Will Dispute This
After 9/11, NORAD and other sources will claim that NORAD’s Northeast Air Defense Sector (NEADS) is notified at this time that Flight 175 has been hijacked. [Washington Post, 9/12/2001; CNN, 9/17/2001; North American Aerospace Defense Command, 9/18/2001; Associated Press, 8/19/2002; Newsday, 9/10/2002] However, the FAA’s New York Center, which is handling Flight 175, first alerts its military liaison about the hijacking at around 9:01 (see 9:01 a.m.-9:02 a.m. September 11, 2001). In addition, according to the 9/11 Commission, NEADS is not informed until two minutes later (see (9:03 a.m.) September 11, 2001). [9/11 Commission, 6/17/2004 ] According to the Commission, the first “operational evidence” that there is something wrong on Flight 175 is not until 8:47, when its transponder code changes (see 8:46 a.m.-8:47 a.m. September 11, 2001), and it is not until 8:53 that the air traffic controller handling it concludes that Flight 175 may be hijacked (see 8:51 a.m.-8:53 a.m. September 11, 2001). [9/11 Commission, 7/24/2004, pp. 7, 21-22]
Shortly After 8:42 a.m. September 11, 2001: Flights 11 and 175 Nearly Crash into Each Other
According to an employee at the FAA’s Boston Center in Nashua, New Hampshire, Flight 11 and Flight 175 nearly crash into each other while heading toward their targets in New York. The unnamed employee says, “The two aircraft got too close to each other down by Stewart” International Airport, which is in New Windsor, NY, about 55 miles north of New York City. Describing the incident, the Nashua Telegraph says that the terrorists “nearly had their plans dashed when the two planes almost collided.” [Telegraph (Nashua), 9/12/2001; Associated Press, 9/13/2001; United Press International, 9/13/2001] It is unclear exactly when this incident occurs, though it is presumably shortly after 8:42, when Flight 175 has its last communication with air traffic control. [9/11 Commission, 7/24/2004, pp. 7]
8:45 a.m.-9:37 a.m. September 11, 2001: Secret Service Does Not Use Its Stinger Missiles to Protect New York and Washington
In New York, the Secret Service has a Stinger missile secretly stored in the World Trade Center, to be used to protect the president if the city were attacked when he visits it. Presumably it keeps this is in WTC Building 7, where its field office is. [Tech TV, 7/23/2002; Weiss, 2003, pp. 379] Stinger missiles provide short-range air defense against low-altitude airborne targets, such as fix-winged aircraft, helicopters, and cruise missiles. They have a range of between one and eight kilometers. [Federation of American Scientists, 8/9/2000; GlobalSecurity (.org), 4/27/2005] Whether the Secret Service makes any attempt at defending New York from the two attacking planes with its Stinger missile is unknown. The agency is also known to have air surveillance capabilities. These include a system called Tigerwall, which provides “early warning of airborne threats” and “a geographic display of aircraft activity” (see (September 2000 and after)). And according to Barbara Riggs, who is in the Secret Service’s Washington, DC headquarters on this day, the agency is “able to receive real time information about other hijacked aircraft,” through “monitoring radar and activating an open line with the FAA.” [US Department of the Navy, 9/2000, pp. 28 ; PCCW Newsletter, 3/2006; Star-Gazette (Elmira), 6/5/2006] These capabilities would presumably be of use if the Secret Service wanted to defend the World Trade Center. Furthermore, according to the British defense publication Jane’s Land-Based Air Defence, “the American president’s residences in Washington and elsewhere are protected by specialist Stinger teams in case of an aerial attack by terrorist organizations.” [Jane’s Land-Based Air Defence, 10/13/2000] Knight Ridder has previously reported “several sources” telling it, “Stinger missiles are in the Secret Service’s arsenal.” [Knight Ridder, 9/12/1994] And according to the London Telegraph, the Secret Service is “believed to have a battery of ground-to-air Stinger missiles” ready to defend the White House. [Daily Telegraph, 9/16/2001] Flight 77 reportedly comes within four miles of the White House before turning toward the Pentagon. [ABC News, 10/24/2001; USA Today, 8/12/2002] Whether the Secret Service makes any attempt at defending the place with its Stinger missiles is unknown. However, the Washington Post will later claim it is an “urban legend that Stinger missiles are mounted on the White House roof.” [Washington Post, 4/4/2002]
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).
