Shortly after hearing strange noises from the cockpit of Flight 93, Cleveland air traffic controllers notice the plane has descended about 700 feet. John Werth, the controller who is handling the plane, tells the supervisor nearest to him, “I think we have another one [i.e., another hijacking].” He will repeatedly radio the cockpit over the next four minutes, asking the pilot to confirm the hijacking, but receive no response. At 9:30 a.m., Werth begins asking other nearby flights on his frequency if they’ve heard screaming; several say that they have. [Gregor, 12/21/2001 
; 9/11 Commission, 7/24/2004, pp. 28; CBS News, 9/10/2006] The Cleveland Center immediately notifies United Airlines’ headquarters of the loss of communication with Flight 93 (see (9:30 a.m.) September 11, 2001). However, the FAA chain of command is apparently not also immediately informed. And the Cleveland Center will not contact NORAD’s Northeast Air Defense Sector (NEADS) about Flight 93 until 10:07 a.m. (see 10:05 a.m.-10:08 a.m. September 11, 2001). [9/11 Commission, 7/24/2004, pp. 28 and 30]
9:30 a.m. September 11, 2001: Air Traffic Control Notifies United Airlines about Flight 93
The FAA’s Cleveland Center notifies United Airlines’ headquarters, near Chicago, that Flight 93 is not responding to attempted radio contacts. [9/11 Commission, 8/26/2004, pp. 39] Cleveland Center made its last normal communication with Flight 93 at 9:27 (see 9:27 a.m. September 11, 2001). [9/11 Commission, 7/24/2004, pp. 28] After the hijacking began at around 9:28, the controller handling Flight 93, John Werth, tried unsuccessfully to re-establish contact with it. [Gregor, 12/21/2001 ; CBS News, 9/10/2006] The lack of response from Flight 93, combined with the plane’s turning to the east (see (9:36 a.m.) September 11, 2001), will lead United to believe, by 9:36 a.m., that it has been hijacked. [9/11 Commission, 7/24/2004, pp. 456]
9:32 a.m. September 11, 2001: Flight 93 Hijacker Tells Passengers Bomb Is Onboard; Air Traffic Controller Overhears
At the FAA’s Cleveland Center, an air traffic controller hears a transmission, presumably made by Flight 93 hijacker-pilot Ziad Jarrah, stating: “Ladies and gentlemen: Here the captain, please sit down, keep remaining sitting. We have a bomb on board. So, sit.” [9/11 Commission, 7/24/2004, pp. 12; 9/11 Commission, 8/26/2004, pp. 39] As the 9/11 Commission later notes, “Like [Mohamed] Atta on Flight 11, Jarrah apparently did not know how to operate the communication radios; thus his attempts to communicate with the passengers were broadcast on the [air traffic control] channel.” [9/11 Commission, 8/26/2004, pp. 98] While this communication is assumed to have come from Flight 93, an early FAA report states that it came “from an unknown origin.” [Federal Aviation Administration, 9/17/2001 ] According to Newsweek, just prior to the communication, Cleveland Center controllers heard the sound of screaming from the flight. [Newsweek, 9/22/2001] The 9/11 Commission states that, around the time of the transmission, the plane’s cockpit voice recording indicates “that a woman, most likely a flight attendant, was being held captive in the cockpit. She struggled with one of the hijackers who killed or otherwise silenced her.” [9/11 Commission, 7/24/2004, pp. 12; 9/11 Commission, 8/26/2004, pp. 39] Though the Cleveland air traffic controller understands the hijacker’s communication, he responds to it: “Calling Cleveland Center, you’re unreadable. Say again, slowly.” He also notifies his supervisor who passes the information up the chain of command, and the FAA’s Command Center is subsequently informed, “United 93 may have a bomb on board.” At 9:34 the Command Center will relay this information to FAA headquarters (see 9:34 a.m. September 11, 2001). [9/11 Commission, 7/24/2004, pp. 28]
9:35 a.m. September 11, 2001: Silent Flight 93 Climbs and Drops; NORAD Still Not Notified
When Flight 93 is over Youngstown, Ohio, Stacey Taylor and other Cleveland flight controllers see it rapidly climb 6,000 feet above its assigned altitude of 35,000 feet and then rapidly descend. The plane drops so quickly toward Cleveland that the flight controllers worry they might be the target. Other accounts say the climb occurs around 9:35 a.m. Controllers continue to try to contact the plane but still get no response. [Guardian, 10/17/2001; USA Today, 8/12/2002; 9/11 Commission, 6/17/2004 ]
9:36 a.m. September 11, 2001: Cleveland Flight Control Wants NORAD Notified; FAA Command Center Says People Are Working on It
According to the 9/11 Commission, at about this time Cleveland flight control specifically asks the FAA Command Center whether someone has requested the military to launch fighters toward Flight 93. Cleveland offers to contact a nearby military base. The Command Center replies that FAA personnel well above them in the chain of command have to make that decision and are working on the issue. [9/11 Commission, 6/17/2004 ] Cleveland overheard a hijacker say there was a “bomb on board” at 9:32 a.m. and passed the message to FAA higher ups (see (9:32 a.m.) September 11, 2001). According to John Werth, the Cleveland controller handling Flight 93, “Within three or four minutes, probably, of when [the hijacking] happened, I asked if the military was advised yet. Had anybody called the military? They said, ‘don’t worry. That’s been taken care of,’ which I think to them, meant they had called the command center in Washington.” [CBS News, 9/10/2006]
9:36 a.m. September 11, 2001: Cleveland Center Receives Numerous Bomb Threats Concerning Planes
According to a book about the FAA’s response to the 9/11 attacks, Cleveland Center air traffic controllers follow Flight 93 as it turns south and reverses course (see (9:36 a.m.) September 11, 2001). But, “bomb threats called in concerning four other planes focused their attention onto what they believed to be more critical maneuvers.” [Freni, 2003, pp. 40] One of these four planes is presumably Delta Flight 1989, which is mistakenly thought to be hijacked and to have a bomb aboard (see (9:28 a.m.-9:33 a.m.) September 11, 2001). [WKYC, 9/11/2006] The identities of the other three planes are unknown. By this time, Cleveland Center has already overheard a radio transmission from Flight 93 stating, “We have a bomb on board” (see (9:32 a.m.) September 11, 2001), and has acknowledged this, reporting, “United 93 may have a bomb on board,” so it seems unlikely that other threatened aircraft would be regarded as “more critical maneuvers.” [9/11 Commission, 6/17/2004 ]
9:39 a.m. September 11, 2001: Flight 93 Hijacker Again Warns of Bomb on Board, Flight Controllers Again Overhear; NORAD Still Not Notified
The Flight 93 hijackers (probably inadvertently) transmit over the radio: “Hi, this is the captain. We’d like you all to remain seated. There is a bomb on board. And we are going to turn back to the airport. And they had our demands, so please remain quiet.”
[Boston Globe, 11/23/2001; Longman, 2002, pp. 209; MSNBC, 9/3/2002; 9/11 Commission, 6/17/2004 ] The controller responds, “United 93, understand you have a bomb on board. Go ahead,” but there is no response. There was a very similar “bomb on board” warning from the same flight at 9:32 a.m. (see (9:32 a.m.) September 11, 2001). The 9/11 Commission indicates that these are separate incidents. [9/11 Commission, 6/17/2004 ] Cleveland flight control apparently continues to wait for FAA superiors to notify NORAD. Earlier in the morning, Boston flight control directly contacted NORAD (see (8:37 a.m.) September 11, 2001) and local air force bases when they determined Flight 11 was hijacked.
9:40 a.m. September 11, 2001: Cleveland Center Notifies Regional Operations Center about Flight 93
The FAA’s Cleveland Center notifies the FAA’s Great Lakes Regional Operations Center about the screams and statements it heard from an unknown origin, but that are believed to have come from Flight 93. These transmissions were heard between 9:28 and 9:39 (see (9:28 a.m.) September 11, 2001, (9:32 a.m.) September 11, 2001 and (9:39 a.m.) September 11, 2001). [Federal Aviation Administration, 9/17/2001 ] The FAA’s Herndon Command Center and Washington headquarters were alerted to Flight 93 several minutes earlier (see 9:34 a.m. September 11, 2001). [9/11 Commission, 8/26/2004, pp. 39]
9:40 a.m. September 11, 2001: Flight 93 Transponder Signal Turned Off; Flight Still Closely Tracked
The transponder signal from Flight 93 ceases. [CNN, 9/17/2001; MSNBC, 9/3/2002; MSNBC, 9/11/2002; 9/11 Commission, 6/17/2004 ] However, the plane can be—and is—tracked using primary radar by Cleveland flight controllers and at United headquarters. Altitude can no longer be determined, except by visual sightings from other aircraft. The plane’s speed begins to vary wildly, fluctuating between 600 and 400 mph before eventually settling around 400 mph. [Longman, 2002, pp. 77, 214; 9/11 Commission, 6/17/2004 ]
After 9:40 a.m. September 11, 2001: NEADS Talks to Cleveland Flight Control about Hijacking, United 93 Not Mentioned
After learning that Delta flight 1989 may have been hijacked from Boston flight control (see 9:39 a.m. September 11, 2001), NEADS calls Cleveland flight control, which is handling the flight, to discuss this. [9/11 Commission, 7/24/2004, pp. 14] Although Cleveland flight control has been aware that United 93 has been hijacked since before 9:30, it apparently fails to mention this to NEADS. According to the 9/11 Commission, the NMCC is not notified of United 93’s hijacking until 10:03 (see 10:03 a.m. September 11, 2001).
