On the morning of Tuesday, September 11, 2001, Islamist militant organization al-Qaeda, led by Osama bin Laden, hijacked four commercial airliners in the United States and tried to crash them into large buildings, succeeding in three cases. American Airlines Flight 11, having departed from Logan International Airport in Boston, was flown into the North Tower of the World Trade Center at 08:46. United Airlines Flight 175, also leaving from Boston, struck the South Tower at 09:03. American Airlines Flight 77, from Dulles International Airport, hit the Pentagon at 09:37. United Airlines Flight 93, from Newark International Airport, was crashed near Shanksville, Pennsylvania, at 10:03, after the passengers on board revolted.
Standing orders on September 11 dictated that, on receiving a request for help from the Federal Aviation Administration (FAA), the North American Aerospace Defense Command (NORAD) would normally order escort aircraft to approach and follow an aircraft that was confirmed to be hijacked in order to ensure positive flight following, report unusual observations, and help in search and rescue in an emergency. The 9/11 Commission determined that, on the morning of September 11, the FAA had not notified NORAD of the hijackings of Flights 11, 77, 93, and 175 in time for escort aircraft to reach the hijacked flights. Notification of the hijacking of Flight 11 prompted the scrambling of two fighter jets from Otis Air National Guard Base, but they were not in the air until after Flight 11 had hit the North Tower. An erroneous FAA report of a hijacked plane heading towards Washington ("phantom Flight 11") prompted the scrambling of three fighters from the 1st Fighter Wing at Langley Air Force Base, which, because of "poor communications", flew east, out to sea, not toward Washington, significantly delaying their arrival on the scene.
Radar tracking On taking control of the airliners, the hijackers of the four planes switched off the transponders or changed their codes, making it difficult to track them on radar. Northeast Air Defense Sector (NEADS) / NORAD personnel stated they had trouble identifying and tracking the aircraft, succeeding only sometimes:
NEADS technicians spotted Flight 11 twenty miles north of Manhattan, two or three minutes before it crashed into the north tower of the World Trade Center. "Looking at the general capitol area, one of the [NEADS] tracker techs thinks he spots the plane on radar." The 9/11 Commission Report: "Radar techs at NEADS/Rome are tracking Flight 77 near Washington, D.C."
Because the transponders in three of the four hijacked aircraft were switched off, and the remaining aircraft had changed its transponder code twice, the FAA had difficulty relaying the current aircraft positions to NORAD/NEADS by phone: even though they had access to the same radar data, NEADS could not find most of the flights. The intermittent data were of some use to the United States Secret Service. Barbara Riggs, then deputy director of the Secret Service, stated, "Through monitoring radar and activating an open line with the FAA, the Secret Service was able to receive real[-]time information about other hijacked aircraft. We were tracking two hijacked aircraft as they approached Washington, D.C."
Flight 11
At 08:13, the pilots of Flight 11 responded to an instruction to turn 20 degrees to the right issued from Boston Center. A few seconds later, Boston Center instructed the pilots to ascend in altitude to which there was no response. Multiple attempts to contact the flight went unanswered and as it became apparent that Flight 11 began to pose an air hazard, air traffic controllers began to reroute arriving aircraft for adequate separation. Boston Center flight controller Tom Roberts said "We had pretty much moved all the airplanes from Albany, New York to Syracuse, New York out of the way because that's the track he was going on." At 08:19, Betty Ong, a flight attendant on Flight 11, called the American Airlines reservation desk to report that the flight was hijacked. At 08:21, Flight 11 stopped transmitting its transponder information concerning its altitude or identification.
At 08:24, the controller heard what he believed was the voice of a hijacker (believed to be Mohamed Atta) in a radio transmission from Flight 11. Two minutes later, the plane veered off course and turned south near Albany, New York. The Boston Center called the FAA Command Center at Herndon at 08:28 to report the hijacking. At 08:32, Herndon called FAA Headquarters in Washington. At 08:34, Boston Center contacted Otis Air National Guard (ANG) base to notify them of the hijacking. The controller at Otis directed Boston to contact NORAD's Northeast Air Defense Sector (NEADS), and then informed the Otis Operations Center to expect a call from NEADS ordering a scramble. At this time two pilots began to suit up and drove to their waiting F-15 fighter jets. At 08:37, Boston Center contacted NEADS in Rome, New York. This was the first report of a hijacking that reached NORAD.
Two F-15 alert aircraft at Otis Air National Guard Base in Falmouth, Massachusetts were ordered to battle stations (seated in their aircraft, engines not yet started). At 08:46, just as Flight 11 struck the North Tower of the World Trade Center, the two F-15s were ordered to scramble (an order that begins with engine start-up, a process that takes about five minutes), and radar confirmed they were airborne by 08:53. By that time, however, the World Trade Center's North Tower had already been hit.
At that time, NEADS personnel were still trying to pinpoint the location of Flight 11, but since the plane had already struck the North Tower, they were unable to. Without having a specific target located, military commanders were uncertain where to send the fighters. Boston Center controllers were still tracking Flight 11 as a primary target but were unable to communicate its location to NEADS by phone.Lynn Spencer, Touching History, p.40
After news of an aircraft hitting the World Trade Center began spreading, no decision was made to alter the course of the F-15s of the 102nd Fighter Wing. A decision was made to send the Otis fighters south of Long Island rather than straight to New York City, as originally ordered by Maj. Nasypany of NEADS.
One of the two pilots, Lieutenant Colonel Timothy “Duff” Duffy, would later state he had already heard about the suspected hijacking (attributed to a phone call from the FAA's Boston Center) as he was supervising training exercises at Otis ANG base. Claiming to have a "bad feeling about the suspected hijacking", he and his wingman, Major Daniel “Nasty” Nash, decided to use their F-15s' afterburners.
Flying supersonically, the F-15s were just south of Long Island when United Airlines Flight 175 hit the World Trade Center's south tower. NEADS wanted to direct the fighters over Manhattan, but FAA air controllers, fearing collisions with civilian aircraft, told NEADS to hold off. According to the FAA, there is an average of 200 flights per 24 hours over the Hudson River in the vicinity of NYC. The fighters were then ordered in a holding pattern off the coast of Long Island (in military-controlled airspace), where they remained from 09:09 to 09:13. After the airspace was cleared, the Otis fighters were directed towards Manhattan, where they arrived at 09:25 and established a combat air patrol (CAP).
The 9/11 Commission report stated the Boston center tried to contact a former alert site in New Jersey, but it had been phased out. The report stated there were only seven "alert" sites (sites which had a pair of aircraft armed and on hand) in the United States by 9/11 and just two in the Northeast Air Defense Sector—Otis Air National Guard base in Massachusetts and Langley Air Force Base in Virginia.9/11 Commission Report pp. 17, 20
Flight 175 United Airlines Flight 175 departed Logan Airport at 08:14 also bound for Los Angeles just like Flight 11. At 08:42, when Flight 175's pilots sent their last radio transmission, the aircraft's transponder was at that time transmitting the assigned code. Five minutes later, the transponder code changed twice, the first indication that the plane had been hijacked, although air traffic controllers would not notice for several more minutes. As word began spreading about the hijacking of Flight 11, air traffic controller David Bottiglia and other controllers searched the radar, looking for Flight 11. At 08:51, he noticed that Flight 175 had changed its transponder.Gregor, Joseph A. Air Traffic Control Recording (UAL 175). National Transportation Safety Board. December 21, 2001 He asked another controller to take over all of his other planes.
Bottiglia tried six times to contact Flight 175 between 08:51 and 08:55, with no response. The aircraft deviated from its assigned altitude at 08:51, and began its turn toward New York City at 08:52.Ritter, Jim. Flight Path Study – United Airlines Flight 175. National Transportation Safety Board. February 29, 2002 At 08:55, Bottiglia told a manager at FAA New York Center that he thought Flight 175 had been hijacked. According to the 9/11 Commission report, this manager then "tried to contact regional managers but was told that they were discussing hijacked aircraft (presumably Flight 11) and refused to be disturbed." At around this time, Flight 175 flew within about 200 feet of Delta Air Lines Flight 2315, bound from Bradley to Tampa, Florida.
In the final moments before impact, according to eyewitness and Newark air traffic controller Rick Tepper, Flight 175 executed ".. a hard right bank, diving very steeply and very fast. As he was coming up the Hudson River, he made another hard left turn ..." One or two minutes before it crashed into the World Trade Center, Flight 175 narrowly avoided a mid-air collision with Midwest Airlines Flight 7 (Midex 7).Spencer, Touching History At 09:01, a New York Center manager called FAA Command Center at Herndon. NEADS was notified at 09:03, when the New York Center manager called them directly, at about the time that Flight 175 hit the South Tower. The F-15s were still 20 minutes away from Manhattan when United Airlines Flight 175 impacted the WTC's south tower.
Although NORAD knew of no other hijacked aircraft, a precautionary measure was taken by ordering fighters at Langley Air Force Base to battle stations.
Phantom Flight 11 At 09:21, NEADS received another call from Colin Scoggins, who reported erroneously that Flight 11 was not, in fact, the aircraft that hit the North Tower at 08:46, as had been previously believed, but that it was still in the air and heading towards Washington. NEADS responded to this report by giving a scramble order to three fighters from the 119th Fighter Wing on alert at Langley Air Force Base at 09:24, and by 9:30 they were in the air.US Air Defense’s Response To The September 11 Attacks: Known And Unknown Facts https://theaviationist.com/2011/09/07/9-11/ According to the 9/11 commission, the Langley pilots were never briefed by anyone at their base about why they were being scrambled, so, despite Langley officials' having been given the order from NEADS to fly to Washington, the unbriefed pilots ended up following their normal training flight plan, due east, out to sea. The fighters then flew north-west towards Washington, arriving around 10:00.
Flight 77