This is another mistake everyone makes. Everyone says steel beams melt at 2700 F degrees. This is true and jet fuel cannot melt steel especially in an open area that is not shaped to concentrate the heat like a furnace. Sounds like a great point right? What is the flaw in this point? It's simple: You DO NOT need to melt steel to have the structure collapse. You just have to heat it enough to weaken it and it will come down on it's own. It's actually MUCH MUCH worse than that as follows: 1) The kinetic energy of the plane did A LOT of damage externally AND internally. First, the outer beams were literally sliced through losing a huge amount of structural rigidity. As well, the mass of the 747 did a huge amount of damage to the internal beams. Who knows how many were sliced through, damaged, bent, protective cladding stripped and so forth. 2) Most people think the WTC towers were normal sized towered. They were not. I saw them in person, each one was about a block wide / long and 94 stories tall. WTC towers were up to 2.5 times the size of the average tower / sky scraper in the average city in North America. This is important because most people have never ever seen 80 story buildings. Most city buildings top out at 40 stories, the vast majority are between 15 and 25 stories. When most people think about WTC building they are thinking like 35 story buildings tops. Here is the problem: Watch the videos and watch where the planes hit the buildings. On each of the buildings, THE REMAINING UNCUT / DAMAGED steel beams had to support 20 to 30 stories of building. And these werent empty stories of concrete. These were full of equipment, furniture and people and things. So, when the outer beams were cut and the inner circle of beams were damaged, the fuel that managed to burn did not even have to come close to melting steel beams, all they had to do is weaken them enough so that they could no longer support 20 to 30 stories of building above them. It is absolutely trivial to see how WTC buildings can start to collapse once you consider the absurd size of the buildings.