Original sentence: On that morning, 19 members of al-Qaeda hijacked four commercial passenger jet airliners.The September 11 attacks (often referred to as 9/11, pronounced nine-eleven) were a series of coordinated attacks by al-Qaeda on the United States on September 11, 2001
Edited sentence: On that morning, 19 al-Qaeda terrorists hijacked four commercial passenger jet airliners.The September 11 attacks (often referred to as 9/11, pronounced nine-eleven) were a series of coordinated attacks by al-Qaeda in the United States on September 11, 2001