There were a total of 19 hijackers involved in the September 11, 2001 attacks. These hijackers took control of four commercial airliners-two Boeing 757s and two Boeing 767s. Three of the flights had five hijackers each, and the fourth flight had four hijackers, making a total of 19 hijackers

. To summarize:

• American Airlines Flight 11: 5 hijackers
• United Airlines Flight 175: 5 hijackers
• American Airlines Flight 77: 5 hijackers
• United Airlines Flight 93: 4 hijackers

Total hijackers: 19