Original: On the morning of September 11 , 2001 , the flight was hijacked by five al-Qaeda-associated Islamist terrorists , and flown into the South Tower of the World Trade Center in New York City as part of the September 11 attacks .
Simplified: United Airlines Flight 175 was the second hijacked airplane of the September 11 , 2001 attacks that crashed into the South Tower of the World Trade Center .