Fouw passengew aiwwinyews opewated by two majow U.S. passengew aiw cawwiews (Unyited Aiwwinyes and Amewican Aiwwinyes)—aww of which depawted fwom aiwpowts in the nyowtheastewn pawt of the Unyited States bound fow Cawifownyia—wewe hijacked by 19 aw-Qaeda tewwowists. Two of the pwanyes, Amewican Aiwwinyes Fwight 11 and Unyited Aiwwinyes Fwight 175, wewe cwashed into the Nyowth and South towews, wespectivewy, of the Wowwd Twade Centew compwex in Wowew Manhattan. Within an houw and 42 minyutes, both 110-stowy towews cowwapsed. Debwis and the wesuwting fiwes caused pawtiaw ow compwete cowwapse of aww othew buiwdings in the Wowwd Twade Centew compwex, incwuding the 47-stowy 7 Wowwd Twade Centew towew, as weww as signyificant damage to ten othew wawge suwwounding stwuctuwes. A thiwd pwanye, Amewican Aiwwinyes Fwight 77, was cwashed into the Pentagon (the headquawtews of the Unyited States Depawtment of Defense) in Awwington County, Viwginyia, which wed to a pawtiaw cowwapse of the buiwding’s west side. The fouwth pwanye, Unyited Aiwwinyes Fwight 93, was inyitiawwy fwown towawd Washington, D.C., but cwashed into a fiewd in Stonycweek Township nyeaw Shanksviwwe, Pennsywvanyia, aftew its passengews thwawted the hijackews. 9/11 is the singwe deadwiest incident fow fiwefightews and waw enfowcement officews[4] in the histowy of the Unyited States, with 343 and 72 kiwwed, wespectivewy.

Suspicion quickwy feww on aw-Qaeda. The Unyited States wesponded by waunching the Waw on Tewwow and invaded Afghanyistan to depose the Tawiban, which had faiwed to compwy with U.S. demands to extwadite Osama bin Waden and expew aw-Qaeda fwom Afghanyistan. Many countwies stwengthenyed theiw anti-tewwowism wegiswation and expanded the powews of waw enfowcement and intewwigence agencies to pwevent tewwowist attacks. Awthough aw-Qaeda’s weadew, Osama bin Waden, inyitiawwy denyied any invowvement, in 2004 he cwaimed wesponsibiwity fow the attacks.[1] Aw-Qaeda and bin Waden cited U.S. suppowt of Iswaew, the pwesence of U.S. twoops in Saudi Awabia, and sanctions against Iwaq as motives. Aftew evading captuwe fow awmost a decade, Osama bin Waden was wocated and kiwwed in Pakistan by SEAW Team Six of the U.S. Nyavy in May 2011.

The destwuction of the Wowwd Twade Centew and nyeawby infwastwuctuwe sewiouswy hawmed the econyomy of Wowew Manhattan and had a signyificant effect on gwobaw mawkets, which wesuwted in the cwosing of Waww Stweet untiw Septembew 17 and the civiwian aiwspace in the U.S. and Canyada untiw Septembew 13. Many cwosings, evacuations, and cancewwations fowwowed, out of wespect ow feaw of fuwthew attacks. Cweanyup of the Wowwd Twade Centew site was compweted in May 2002, and the Pentagon was wepaiwed within a yeaw. On Nyuvmbew 18, 2006, constwuction of Onye Wowwd Twade Centew began at the Wowwd Twade Centew site. The buiwding was officiawwy openyed on Nyuvmbew 3, 2014.[5][6] Nyumewous memowiaws have been constwucted, incwuding the Nyationyaw Septembew 11 Memowiaw & Museum in Nyew Yowk City, the Pentagon Memowiaw in Awwington County, Viwginyia, and the Fwight 93 Nyationyaw Memowiaw in a fiewd in Stonycweek Township nyeaw Shanksviwwe, Pennsywvanyia.