Why did the Twin Towers collapse?

Answer 1

The Twin Towers of the World Trade Center collapsed because when the planes were flown into the towers it ignited the jet fuel and after burning for hours it made the inner columns weaken and made the outer structure weaken, so basically the inner columns of the impact zone couldn't support the upper floors and gave way pancaking one floor at a time in a 10 second radius.
The Twin Towers of New York's World Trade Center were targeted as part of a terrorist campaign against the United States by Islamic fundamentalists opposed to the US actions in the Middle East. The attack was funded in part by the Al Qaeda movement led by Osama bin Laden (also Usama), a Saudi expatriate who became active in guerrilla and terrorist movements.

The attacks on the Pentagon, in NYC, and in Pennsylvania took place on September 11, 2001. At 8:46 AM EDT, American Airlines Flight 11 was crashed into the World Trade Center's North Tower, followed by United Airlines Flight 175, which hit the South Tower at 9:03 AM. The South Tower collapsed less than an hour later at 9:59 AM, followed by the North Tower at 10:28 AM. As many as 2750 people, including the hijackers and passengers of the two planes, were killed.

The Collapses

The South tower collapsed at 9:59 and buckled into the damaged section where the plane had hit. It did not fall over, but continued to lean at a slight angle as it pulverized a large part of the lower floors. Along one side, the lower seven floors were left partially standing, mainly along the exterior stairwells that had been reinforced after the bombing in 1993.

The North Tower collapsed at 10:28 and caved in from two sides, moving downward through the center with less tilt than the South Tower. It continued collapsing until many of the lower floors were crushed into the basements. The highest part, the tall TV mast, broke free at some point and was carried under some of the rubble.