If you watch the videos, you can see what are called squibs being exploded on the side of the building. Typically used in demolition, as the tower came down puffs of smoke coming out the sides lead the top of the tower to the ground. Watch any demolition of any building and they match the ones at 9/11. Also, about 6 weeks before it happened, the building underwent a power down. Meaning, no security cameras, no lights, nothing. It wasn't planned either. No one was told of the power down in advance. This was supposed to be when they were installing the new "security system". Witnesses say that they saw mean with big boxes and running wire everywhere, so you know not real suspicious. You need to run wire for a new security system blah blah blah.
As far as the planes burning jet fuel causing the building to collapse. Remember that 3 hour long fire that happened in the 70s in the WTC buildings? Uh yeah, why didnt they come down then? That fire lasted twice as long as 9/11.
Plus, if you notice there is black smoke coming from the building. Black smoke means that the fire is being deprived of oxygen meaning a smoldering fire. Plus, the heat would have to be atleast 2300 degrees F* to melt the steel. Regular jet fuel only gets to about 1200*F and thats in an out of control situation. You would need an agent called Thermite to melt the steel in the WTC. Thermite, because it gets so hot, it is used in steel factorys to melt the steel and to shape it. There is also a substance called Thermate which is just sulfur added to the substance and gets much hotter than thermite and the results are usually quicker.
Furthermore, a survivor from 9/11 told the news and everyone that there was an explosion in the basement. He felt a boom come from underneath him and then above him. After the explosion, a man ran in from the basement with his skin hanging off of him yelling explosion! explosion! He also mentioned as he was going up the stairwell, he came to the 34th floor which he said at the time was completely empty, nothing was in there. He heard what sounded like a dumpster hitting concrete. If you have ever seen a garbage truck pick up a dumpster and dump it into itself and set it back down. Im guessing thats the noise hes talkin about. He said that sound really scared him b/c he knew nothing was supposed to be on that floor, so he by passed it and went on to try to save other people. The same noises were heard from the other tower before 9/11. One guy says he heard the same noises coming from a floor above him and one day he went to see what it was and found nothing in the room.
After a bomber plane had hit the empire state building, the designers of the WTC actually designed the building to withstand a Boeing 707 crashing into it,the biggest plane at the time of construction.
If you have seen the videos then, what I just typed is just a repeat of everything they said. If you have not seen the videos, whether you belive it or not they are still pretty interesting to watch and I recommend you see them.