Osama bin Laden frequently pressured his team to strike in the spring of 2001. September 11th was ultimately chosen for a chillingly practical reason: it was a Tuesday.
Because the date "9/11" aligns perfectly with the American emergency telephone number, a persistent myth suggests the hijackers chose the day for its symbolic terror. Another popular theory claims al-Qaeda selected the date to mark the anniversary of the 1683 Battle of Vienna. However, the 9/11 Commission Report and interrogations of the plot's mastermind, Khalid Sheikh Mohammed, revealed that these were just coincidences. The timeline was purely a matter of logistical readiness.
Tactical leader Mohamed Atta continually pushed the operation back because the hijacking teams simply were not ready. Several of the "muscle" hijackers—the men tasked with controlling the passengers while the pilots flew the planes—had trouble securing U.S. visas and arrived later than expected. The pilot hijackers also needed more time to complete their cross-country surveillance flights and finalize their operational planning.
By late summer, the teams were finally in place. The choice of a Tuesday in early September was a calculated tactical decision. Commercial airlines typically experience their lowest passenger volumes on Tuesdays. The hijackers specifically targeted transcontinental flights, which carried heavy fuel loads for maximum destruction, but lighter passenger manifests meant less risk of a passenger revolt. At the same time, striking on a weekday morning ensured that the target destinations—the World Trade Center and the Pentagon—would be packed with thousands of workers at their desks.
In late August 2001, once all preparations were complete, Atta selected September 11. He communicated the final date to Ramzi bin al-Shibh, an al-Qaeda coordinator, using a coded message disguised as a puzzle about two branches, a stick, and a cake with a stick down. The "9-1-1" emergency number coincidence never factored into the planning; in the Middle East and Europe, where the plotters lived and trained, dates are written in a day-month-year format (11/9). The date was merely the earliest Tuesday they were fully prepared to act.