One the leaders of Al Qaeda in Arabian Peninsula, Khubeib As-Sudani narrates an incident prior to September 11 attacks which highlights the intensive secrecy maintained by those who planned the attacks:

One night, while dining at the Ainak Camp near Kabul with Usama bin Laden, one of the brothers said, “O Sheikh, yesterday I saw a dream” and began narrating his dream, “I saw two tall buildings in America and on top of one of them was Khalid Sheikh Mohammad, and he was training the Ghumaida (Ghamidi) brothers Karate who were on top of the second building”

And in fact most of those who took part in the operation were well known by the brothers as Ghumaida (those from the Ghamidi tribe) who were from the south of the Arabian Peninsula. At the time of the dream these brothers were undertaking a special forces training camp.

Usama turned towards Abu Hafs al Misri and asked him to interpret the dream. Abu-Hafs turned towards the brother and said, “It seems yesterday you ate too much beans during dinner”; so as to quietly divert the questioner from the subject of the dream, as it contained details of the operation.