Input (grade 13): 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.
Output (grade 11): 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.