U.S. military response during the September 11 attacks

North American Aerospace Defense Command

Industry	Aerospace defense, Military
Founded	1958
Headquarters	Colorado Springs , United States
Products	Aerospace warning, aerospace control, and maritime warning for North America

On the morning of September 11, 2001, the Islamist extremist organization al-Qaeda seized control of four U.S. commercial airplanes, successfully crashing three into prominent landmarks. American Airlines Flight 11, which departed from Boston, collided with the North Tower of the World Trade Center at 08:46. United Airlines Flight 175, also originating from Boston, struck the South Tower at 09:03. Meanwhile, American Airlines Flight 77, departing from Washington Dulles International Airport, crashed into the Pentagon at 09:37. The fourth plane, United Airlines Flight 93, flying out of Newark Liberty International Airport, was brought down near Shanksville, Pennsylvania, at 10:03 after passengers attempted to overpower the hijackers.

According to established procedures on that day, the North American Aerospace Defense Command (NORAD) was to deploy fighter jets to intercept any confirmed hijacked aircraft upon FAA notification for tracking and emergency intervention. However, the 9/11 Commission revealed that the FAA failed to alert NORAD promptly about the hijackings of Flights 11, 77, 93, and 175. Fighter jets dispatched from Otis Air National Guard Base took off only after Flight 11 had already crashed into the North Tower. Furthermore, a mistaken FAA report indicating a hijacked plane heading toward Washington caused fighters from the 1st Fighter Wing at Langley Air Force Base to divert east over the ocean due to communication breakdowns, significantly delaying their response.

Radar tracking

Following the hijackings, the perpetrators either turned off transponders or altered their codes, making radar detection more difficult. Personnel at the Northeast Air Defense Sector (NEADS) and NORAD reported sporadic success in locating these aircraft:

• NEADS operators detected Flight 11 approximately twenty miles north of Manhattan shortly before it impacted the World Trade Center’s North Tower.
• Radar specialists at NEADS in Rome tracked Flight 77 near the Washington, D.C. area.

With transponders disabled or modified, the FAA encountered challenges in providing NORAD/NEADS with precise aircraft locations despite sharing radar information. These intermittent tracking updates assisted the United States Secret Service in monitoring two hijacked planes approaching Washington, D.C.

Flight 11

At 08:13, pilots of Flight 11 acknowledged a turn instruction issued by Boston Center but soon ceased communication. When contact attempts failed and the plane became a potential threat, controllers rerouted other air traffic away from its path. Flight attendant Betty Ong reported the hijacking at 08:19. By 08:21, Flight 11 had stopped transmitting transponder signals.

A suspicious voice was picked up on radio transmissions at 08:24 as the aircraft deviated southward near Albany, New York. Boston Center informed FAA Command and FAA Headquarters by 08:32 and contacted Otis Air National Guard Base at 08:34 regarding the hijacking. Otis instructed Boston to reach out to NEADS in Rome, New York; two pilots began preparing F-15 fighters for immediate deployment.

By 08:37, Boston Center's report reached NORAD. Although two F-15s stationed at Otis ANG Base were placed on alert, they were not scrambled until 08:46—after Flight 11 had already struck the World Trade Center’s North Tower—and took off by 08:53. NEADS was still attempting to locate Flight 11 and could not direct interceptors without confirmation of its position.

Despite confirmation of the crash, no immediate redirection occurred for the Otis-based F-15s; instead, they were sent south of Long Island rather than directly toward New York City. Lieutenant Colonel Timothy “Duff” Duffy and Major Daniel “Nasty” Nash accelerated their F-15s using afterburners upon receiving news of the hijacking.

While flying supersonic near Long Island at the time United Airlines Flight 175 hit the South Tower, NEADS tried to guide fighters over Manhattan but FAA controllers delayed clearance due to concerns over civilian air traffic—approximately two hundred daily flights use that airspace. The fighters remained near Long Island from 09:09 to 09:13 before receiving approval to conduct combat air patrol over Manhattan by 09:25.

The 9/11 Commission highlighted that only seven alert facilities with armed aircraft existed across the country on September 11, including just two within the Northeast Air Defense Sector—Otis ANG Base and Langley Air Force Base—restricting options for rapid military engagement.

Flight 175

United Airlines Flight 175 took off from Logan Airport at 08:14, heading to Los Angeles like Flight 11. At 08:42, the crew transmitted their final radio message while the transponder continued to send the designated code. Five minutes later, the transponder code was altered twice, indicating a hijacking, although air traffic controllers did not immediately detect this. As information about Flight 11’s hijacking circulated, air traffic controller David Bottiglia scanned radar for Flight 11 and noticed at 08:51 that Flight 175 had changed its transponder code. He reassigned his other aircraft to a different controller.

Between 08:51 and 08:55, Bottiglia made six unsuccessful attempts to establish contact with Flight 175. The aircraft departed from its assigned altitude at 08:51 and altered course toward New York City at 08:52. At 08:55, Bottiglia notified an FAA New York Center manager of his suspicion that a hijacking was underway; however, the manager declined to be disturbed due to ongoing discussions among regional managers regarding hijacked planes (likely Flight 11). Around this period, Flight 175 passed roughly 200 feet from Delta Air Lines Flight 2315.

In its final moments, eyewitness accounts and Newark air traffic controller Rick Tepper described Flight 175 performing "a sharp right bank, diving steeply and rapidly," followed by a sharp left turn as it neared the Hudson River. One or two minutes prior to crashing into the World Trade Center, it narrowly avoided colliding mid-air with Midwest Airlines Flight 7. At 09:01, a New York Center manager alerted the FAA Command Center; NEADS was informed at 09:03—approximately when Flight 175 impacted the South Tower. The F-15 fighter jets were still about twenty minutes away from Manhattan at the time of impact.

Despite NORAD lacking awareness of additional hijacked aircraft, fighter jets at Langley Air Force Base were placed on alert as a precautionary measure.

Phantom Flight 11

At 09:21, NEADS received an erroneous report from Colin Scoggins asserting that Flight 11 remained airborne and was en route to Washington instead of having crashed into the North Tower at 08:46. NEADS dispatched three fighters from the 119th Fighter Wing at Langley Air Force Base at 09:24; these jets were airborne by 09:30. According to the 9/11 Commission, pilots from Langley were never informed of the scramble’s actual purpose and initially followed their standard training route eastward over the ocean before turning northwest toward Washington, arriving around 10:00.

Flight 77

American Airlines Flight 77 took off from Dulles International Airport at 08:20. Its final communication was recorded at 08:50:51. The flight proceeded normally until 08:54, when it veered southward, departing from its designated route. At 08:56, the aircraft's transponder was deactivated, resulting in loss of radar tracking. Following reports of hijacked planes crashing into the World Trade Center, Indianapolis Center suspected Flight 77 had also been seized and promptly alerted the FAA Command Center located in Herndon, which then contacted FAA Headquarters at 09:25.

NEADS became aware of the missing flight at 09:34 during a conversation with FAA Headquarters.

Washington Center: Let me inform you—we have also lost American 77... They lost all contact with it. There is no information on its whereabouts or what has occurred.

The FAA did not initiate this alert; instead, NEADS reached out to FAA in an attempt to track what was initially referred to as Phantom Flight 11 (see prior section).

At 09:35, Boston Center informed NEADS that they had identified an aircraft—later verified as Flight 77—rapidly approaching Washington D.C. Two minutes afterward, a NEADS radar technician spotted a target believed to be Flight 77, but it disappeared immediately. NEADS commanded fighter jets stationed at Langley to intercept; however, the plane struck the Pentagon at 09:37:46 before the fighters could arrive, still about 150 miles away.

Flight 93

At 09:28, John Werth, a controller at FAA Cleveland Center, detected possible screaming and observed that Flight 93 had descended approximately 700 feet amid reports of missing passenger planes and attacks on the World Trade Center. At 09:32, a voice declared "We have a bomb on board," which led Werth to notify his supervisor and FAA Headquarters. By 09:36, Cleveland Center inquired with FAA Command Center whether the military had been alerted; the response indicated senior FAA officials were deliberating military involvement. As of 09:49, no decision had been finalized, and NEADS was not contacted until 10:07—four minutes after Flight 93 crashed near Shanksville, Pennsylvania. Werth later recalled:

Within three or four minutes after it happened, I asked if the military had been notified yet. Had anyone contacted them? They replied, "Don't worry, that's been handled," which I interpret as meaning they had contacted the command center in Washington.

Dennis Fritz, director of Johnstown municipal airport, reported receiving multiple calls from the FAA warning about Flight 93’s approach and advising evacuation due to the potential crash.

In the event Flight 93 had reached Washington D.C., Air National Guard pilots Lieutenant Colonel Marc H. Sasseville and Lieutenant Heather Penney were prepared to sacrifice their lives by ramming their unarmed F-16 fighter jets into it.

NORAD timeline

On September 18, 2001, NORAD published a detailed sequence of the September 11 incidents, incorporating times when the FAA made contact. Nevertheless, after examining communication recordings, the 2004 9/11 Commission identified certain inaccuracies within this timeline. This document had served as the official military narrative and was referenced in Air War over America as well as in testimony by NORAD’s Major General Larry Arnold and Colonel Alan Scott in 2003.

In August 2006, The Washington Post revealed that some commission members suspected Pentagon officials of intentionally misleading both the commission and the public. Discussions were underway about potentially pursuing criminal charges due to evidence suggesting false statements aimed at obscuring a flawed response.

Commission chairs Thomas Kean and Lee H. Hamilton, in their book Without Precedent, highlighted that errors in FAA and NORAD accounts contributed to conspiracy theories by exaggerating military response times and scramble alerts.

The NORAD timeline reported earlier FAA notifications than those confirmed by tapes; for instance, it recorded notification of Flight 175’s hijacking at 08:43, whereas actual tapes show NORAD was informed only as Flight 175 struck the South Tower at 09:03. Scoggins noted ongoing uncertainty partly stemmed from American Airlines’ delay in confirming Flight 11’s crash.

According to the 9/11 Commission Report, around 08:32, the FAA’s Herndon Command Center initiated a teleconference linking Boston, New York, and Cleveland Centers to share situational awareness. Boston controllers monitored American Airlines Flight 11 from departure until its crash.

FAA’s mistaken belief that Flight 11 might still be airborne was influenced by American Airlines not confirming loss of contact until after 10:00. The NORAD timeline indicated fighter jets scrambled from Langley at 09:24 following a 09:21 FAA report of Flight 77’s hijacking; however, NORAD did not reference any phantom Flight 11 at that time.

In October 2003, upon discovering withheld materials including a destroyed audio recording of New York controllers’ oral communications on September 11, the Commission subpoenaed FAA documents. The following month, a similar subpoena was issued to NORAD for related reasons.

By July 2004, these issues were referred to Inspectors General within the US Department of Transportation and the Department of Defense to investigate allegations of false testimony.

The Department of Defense Inspector General’s report, released in August 2006, cleared military personnel of deliberate deception but recommended enhancements in event documentation for future incidents.

Likewise, the Transportation Department Inspector General’s report dated August 31, 2006, found no evidence that FAA staff intentionally misled the Commission.

Background

In January 1982, the FAA introduced the National Airspace System (NAS) Plan aimed at upgrading Air Traffic Control capabilities through advanced systems such as Doppler radar improvements, enhanced ground-to-air surveillance, and superior transponder technology. This plan also involved consolidating air route traffic control centers and reducing flight service stations. Within airspace under FAA jurisdiction, responsibility for hijack intercept aircraft rests solely with the FAA; there is no Department of Defense overlap.

Radar modernization efforts at NEADS experienced a substantial cost escalation—an increase of approximately 700% following a contract awarded in 1997—prompting the Air Force to cancel and reissue bids.

Prior to September 11, military exercises accounted for scenarios where terrorists might employ hijacked planes as missiles; however, these drills predominantly involved aircraft originating outside the United States. NORAD and the US Air National Guard held primary responsibility for intercepting hijacked aircraft mainly to support law enforcement agencies. Major General Larry Arnold remarked that attacks originating domestically were generally treated as law enforcement matters. Military aviation assets were tasked with assisting flight monitoring, reporting suspicious activities, and conducting search and rescue operations.

Deputy Attorney General Jamie Gorelick was involved in overseeing these security protocols. In April 2001, NORAD dismissed an exercise proposal simulating a foreign hijacked aircraft striking the Pentagon as unrealistic—just five months prior to an actual attack employing similar tactics. By January 2002, Major General Arnold conceded that military planners had not seriously contemplated hijacked airliners being used in suicide missions.

Post-9/11 Initiatives

In April 2003, a contract was secured to enhance Battle Control Systems, targeting completion by the summer of 2006.

Subsequent technologies, such as the Joint-Based Expeditionary Connectivity Center (JBECC), combine radar data from both civilian and military sources. This integration merges target information collected from airborne, terrestrial, and maritime sensors spanning roughly 400 miles of coastline. The result is highly accurate fire-control tracks that effectively direct interceptor responses.

Retired Major General Larry Arnold of the USAF remarked in May 2001 that JBECC provides "...additional time to launch fighters and detect any target, regardless of size or altitude." He also emphasized post-9/11 funding efforts which included linking FAA radar systems nationwide, deploying compatible radios for command and control communications, and acquiring a new command system that merges radar with communication capabilities. Initial funding of $75 million ultimately expanded to nearly $200 million.

Besides the FAA, entities like airlines, the Department of Defense, NASA, and international partners utilize the FAA’s Enhanced Traffic Management System (ETMS) software and data for managing and monitoring flights.

2009 GAO Assessment of ASA

In January 2009, the Government Accountability Office (GAO) published an evaluation of the Air Force’s Air Sovereignty Alert (ASA) mission:

The Air Force has yet to implement ASA operations in accordance with DOD, NORAD, and Air Force directives that mandate ASA as a continuous (steady-state) mission. It has not completed 140 identified tasks necessary to integrate ASA into planning, programming, and budgeting cycles, instead prioritizing overseas missions. Establishing ASA as a steady-state operation would help alleviate difficulties in balancing homeland defense with warfighting commitments.

The GAO further determined that critical Air Force homeland defense documents fail to clearly define ASA responsibilities or account for operational complexities.

To enhance ASA effectiveness, the GAO advised the Secretary of Defense to instruct NORAD to perform regular risk evaluations identifying ASA requirements—including locations, personnel, and aircraft—and to formally designate ASA responsibilities to appropriate units with comprehensive readiness evaluations.

Additional recommendations directed at the Secretary of Defense included urging the Air Force Secretary to:

• Develop a schedule for adopting ASA as an ongoing mission.
• Revise and enforce ASA program directives consistent with NORAD, DOD, and Air Force policies.
• Update homeland defense doctrines and policies to explicitly clarify ASA functions.
• Integrate ASA considerations into the six-year Future Years Defense Program.
• Formulate strategies addressing capability shortfalls caused by aging F-15 and F-16 fleets.
• Establish formal procedures for rotating deploying units while preserving commanders’ operational flexibility.

See also

• United States government operations and exercises on September 11, 2001