The plan for 9/11 was hatched by KSM in 1996 when it was presented to OBL. At that time it was much bigger. OBL was of the opinion that it was too big to organise and keep secret. The operation was discussed by Osama bin Laden, Kahlid Sheikh Mohammed and Al-Qaeda Chief of Operations Mohammed Atef. That caused the first delay and the operation was scaled down and was given the go ahead by bin Laden from Afghanistan in 1998 or very early in 1999. The first "pilots" were dedicated Jihadists from the Yemen and they were sent to the USA but their english was not good enough and they were not good student pilots, this caused the second delay to the mission.

Late in 1999 Mohammed Atta and four others left Germany and travelled to Afghanistan where they were selected for the operation by Osama bin Laden personally. They were chosen because they were used to living in the west, were proficient in english and it was easier for them to get entry visas to the US from Germany.

The attacks were thought of, planned and financed from Afghanistan. Where those who carrried out the attack were born is irrelevant.