Why did the World Trade Centers fall after being hit by a plane, but the Empire State building didn't?

On the foggy morning of Saturday, July 28, 1945 at 9:49 a.m., the ten-ton, B-25 bomber smashed into the north side of the Empire State Building. The majority of the plane hit the 79th floor, creating a hole in the building eighteen feet wide and twenty feet high. The plane's high-octane fuel exploded, hurtling flames down the side of the building and inside through hallways and stairwells all the way down to the 75th floor.