Review: The September 11, 2001 attacks (often referred to as 9/11) consisted of a series of coordinated terrorists. he hijackers intentionally crashed two of the airliners (United Airlines Flight 175 and American Airlines Flight 11) into the World Trade Center in New York City, one plane into each tower (1 WTC and 2 WTC), resulting in the collapse of both buildings soon afterward and irreparable damage to nearby buildings.Nineteen men boarded the four planes, five each on American Airlines Flight 11, United Airlines Flight 175 and American Airlines Flight 77, four on United Airlines Flight 93. Fifteen of the attackers were from Saudi Arabia, two from the United Arab Emirates, one from Egypt, and one from Lebanon.