Hijackers in the September 11 attacks
The aircraft hijackers in the September 11 attacks were 19 men affiliated with al-Qaeda, a jihadist organization based in the Islamic Emirate of Afghanistan. They hailed from four countries: 15 of them were citizens of Saudi Arabia, two were from the United Arab Emirates, one was from Egypt, and one from Lebanon.
Source: Wikipedia — Hijackers in the September 11 attacks (CC BY-SA 4.0)