Inside the Al-Qaeda cell that hijacked four U.S. airliners and its lingering legal fallout

Al-Qaeda assembled a cell of 26 operatives, 19 of whom commandeered four passenger jets that were used as weapons against the World Trade Center towers, the Pentagon and a field in Pennsylvania. The group’s composition included 18 Saudis, two Emiratis, two Yemenis, and one each from Egypt, Lebanon, Morocco and Pakistan. Five senior planners—Khalid Sheikh Mohammed, Walid Muhammad Salih Mubarak Bin ‘Attash, Ramzi Bin al-Shibh, Ali Abdul Aziz Ali and Mustafa Ahmed Adam al-Hawsawi—were captured in Pakistan and Yemen and are still confined at Guantánamo, facing charges such as murder in violation of the law of war and terrorism.

The piece highlights how lax visa vetting, forged passports and inadequate border checks enabled the conspirators to enter the United States repeatedly, with 22 of 23 visa applications approved and many passports issued within weeks of creation. Despite the 2011 killing of Osama bin Laden, the legal and investigative processes related to the attacks remain unresolved.