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(詳細はSeptember 11, 2001, four commercial airliners were hijacked and deliberately crashed. American Airlines Flight 11, departing from Boston, was flown into the North Tower of World Trade Center at 8:46 a.m. United Airlines Flight 175, also departing from Boston, was flown into the South Tower at 9:03. American Airlines Flight 77, departing from Washington, was flown into the Pentagon at 9:37. United Airlines Flight 93, departing from Newark, crashed near Shanksville, Pennsylvania at 10:03. Standing orders on September 11 dictated that, upon receiving a request for assistance 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 assure positive flight following, report unusual observances, and aid search and rescue in the event of an emergency.〔(【引用サイトリンク】title=Order 7610.4, Special Military Operations )〕 The 9/11 Commission determined that on the morning of September 11, the FAA did not adequately notify NORAD of the hijackings of Flights 11, 175, 77 or 93 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 more fighters from the 1st Fighter Wing at Langley Air Force Base, which due to "poor communications", ended up flying eastward, out to sea, instead of heading toward Washington, significantly delaying their arrival on the scene. ==Radar tracking== The hijackers of the four planes switched off the transponders or changed their codes upon taking control, making it difficult to track them on radar. Northeast Air Defense Sector/NORAD personnel stated they had difficulty identifying and tracking the aircraft, though they were at times able to locate them: *NEADS technicians spotted American Airlines flight 11 twenty miles north of Manhattan, just 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 () 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." As 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, so even though they had access to the same radar data, NEADS was unable to locate most of the flights. This intermittent data was of some use to the US 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."〔(【引用サイトリンク】title=PCCW eNewsletter )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「U.S. military response during the September 11 attacks」の詳細全文を読む スポンサード リンク
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