There are multiple videos that show puffs of smoke and or squibs coming from both towers many floors below the actual point of collapse... Also, there were so-called interior renovations taking place just months prior and up to the date of 911, elevator upgrades and repairs, large electrical upgrades, multiple floors from ground level to the top of both towers were closed off, (all on record)...
The main argument when it comes to the engineering side of this, is that the total lack of structural "resistance" during the towers collapse. The steel inner cores should have created resistance, this means these vertical standing steel beams would have either slowed down the collapse significantly or only sections of the towers should have toppled over and away...
All three buildings show the signs of total infrastructure failure, impossible without first weakening and/or slicing those vertical beams/columns!

The proof is in the video that it was NOT a controlled demolition. First of all, all the controlled demolition footage show the puff of smoke of the demolition charges before the building starts collapsing. The WTC building started collapsing (ie the building above the crash site started moving before the puffs of smoke (caused by the collapsing building compressing the air on the floor that are collapsing...). Either way, look at the footage carefully and you will see this is very clear. If the WTC buildings were wired, then the building shouldn't start collapsing until AFTER the puffs of smoke...

Also if the building was wired to blow, how did they know the precise place to place the charges? And wouldn't they go off when a big plane full of jet fuel it them? C4 will detonate given a high enough temperature, which jet fuel burning will attain.

this clip seriously points to a controlled demo more than alot of the others do has it is so close to the event.eg . you can actually hear each floor being detonated,as well as the strange comparisons too actual recorded demolitions.