[2] He attended two meetings from August 11 to 20 in 1988, along with bin Laden, al-Zawahiri, Mamdouh Mahmud Salim, Jamal al-Fadl, Wa'el Hamza Julaidan, and Mohammed Loay Bayazid and eight others, to discuss the founding of "al-Qaeda".

[14][15][16] While in Sudan, he allegedly conducted a study which resulted in him presenting al-Qaeda details on why aircraft hijackings were a poor idea as they were engineered to allow the negotiation of hostages in exchange for prisoners, rather than inflicting damage.

[19] When Mohammed returned to Afghanistan, he turned to Atef to set up a meeting with bin Laden in Tora Bora, at which he told the pair his plans for military attacks against the United States.

[19] Prior to 1996, Abu Ubaidah al-Banshiri, Atef and Yaseen al-Iraqi aided Enaam Arnaout in purchasing AK-47s and mortar rounds from a Pashtun tribesman named Hajjji Ayoub, and they were subsequently delivered in large trucks to the Jawr and Jihad Wahl training camps.

[21] He drew up a plan summarizing the positive qualities of Taliban leaders, and showed his "nuanced understanding" that the United States had energy interests in the Caspian Sea which would lead them to want an oil pipeline built through Afghanistan in the near future.

[15] In 1998, a number of militants began to speak openly of their disdain for Atef, leading bin Laden to convene a meeting at which he spoke at length about Abu Bakr's loyalty to Muhammad.

[30] Near the end of the year, he met with Ramzi bin al-Shibh, Mohamed Atta and Ziad Jarrah and explained they would be undertaking a highly secret operation, in cooperation with Nawaf al-Hazmi whom he named as Rabia al-Makki.

[15]: 230 In January 2001, in Kandahar, Atef's daughter married bin Laden's 17-year-old son Mohammed; the wedding guests included Osama's mother, al-Jazeera journalist Ahmad Zaidan, a "few" Taliban party members, and about 400 others.

He was not the gregarious type who could live with the young mujahideen and understand and solve their problems and address their concerns ... his work and activities sometimes compelled him to avoid people and keep away from others.Following the September 11, 2001 attacks, and still a fugitive from his U.S. indictment in the 1998 Embassy bombings, Atef appeared on the initial list of the FBI's top 22 Most Wanted Terrorists, which was released to the public by President Bush on October 10, 2001.

[37] In early November 2001, the Taliban government announced they were bestowing official Afghan citizenship on him, as well as bin Laden, Zawahiri, Saif al-Adel, and Shaykh Asim Abdulrahman.

[44] His death was confirmed when the ambassador of the Taliban, Abd Al-Salam Dhaif, said three days later, "Abu Hafs al-Masri died from injuries he suffered after US warplanes bombed his house near Kabul.

[2][52] Under interrogation, a number of suspected militants including Ibn Shaykh al-Libi later invented fictitious ties from Atef to other uninvolved entities to distract American attention from their true colleagues.

[55] In March 2002, Bosnian security forces raided a Benevolence International Foundation office in Sarajevo and seized a computer which contained a number of documents suggesting a degree of complicity with al-Qaeda, including a letter to Atef from Enaam Arnaout stating that "the organization loaned us a howitzer cannon, and it must be returned so that it can be transferred to Kabul".