premise: The World Trade Center was destroyed in September.
hypothesis: The Twin Towers of the World Trade Center collapsed on September 11 , 2001 , as a result of being struck by two jet airliners hijacked by 10 terrorists affiliated with al-Qaeda , during the September 11 attacks . World Trade Center (1973–2001) . It featured landmark twin towers , which opened on April 4 , 1973 , and were destroyed as a result of the September 11 attacks . World Trade Center (2001–present) . They were destroyed on the morning of September 11 , 2001 , when al-Qaeda-affiliated hijackers flew two Boeing 767 jets into the complex in a coordinated act of terrorism .