At 9:03 a.m. EDT on September 11, 2001, five terrorists crashed United Airlines Flight 175 into the southern facade of the South Tower. Three buildings in the World Trade Center complex, including 2 WTC, collapsed due to fire-induced structural failure. The light construction and hollow nature of the structures allowed the jet fuel to penetrate far inside the towers, igniting many large fires simultaneously over a wide area of the impacted floors. The fuel from the planes burned at most for a few minutes, but the contents of the buildings burned over the next hour to hour and a half.