As part of the September 11 , 2001 attacks , two of the four planes hijacked were United planes . One aircraft was N612UA , a Boeing 767 – 200 operating as United Airlines Flight 175 , flown into the South Tower of the World Trade Center . The other was N591UA , a Boeing 757 – 222 operating as United Airlines Flight 93 , which crashed in rural Pennsylvania after the passengers fought back against the hijackers , and was suspected to have been directed towards the United States Capitol building according to the DHS
United Airlines Flight 175
United Airlines Flight 175
History of United Airlines