Watching the news yesterday of a fire collpasing a 4 lane elevated section of I-85 in downtown Atlanta shoud put to rest the structural argument about the Twin Towers collapse. No, jet fuel cannot burn hot enought to "melt" steel (as in turning it into complete liquid form). However, steel loses it's strength in proportion to temerature and duration of the fire. Structural engineering standards are to build things 2 to 4 times breaking strength (depending on the safety factor required). So if structural steel gets hot enough to weaken it beyond the safety factor, it can and will bend, warp, twist or shear depending on the type of load it is supporting. A section of elevated interstate highway completely collapsed yesterday in Atlanta due to a blaze caused by burning PVC conduit stored underneath it (the orange stuff on a roll they use to bury underground cable). An interstate overpass is made of steel-reinforced concrete supported by steel I-beams. Not a whole lot different structurally than a skyscraper (except that the I-beams are supporting a shear load vs. a compression load). On top of jet fuel, there was a whole lot of plastic (carpeting, cubicle desks, plumbing, electrical insulation) plus combustible fiber (paper, drywall, boxes) that burned for 30 minutes or more before the Twin Towers collapse. Plenty of heat and time to sufficiently weaken structural steel to it's failure point. Now for CIA/Bin Laden/Saudia Arabia conspiracy theories, those are potentially still on the table. But it doesn't take thermite to bring down a building or a highway. This is simple engineering statics and dynamics 101, acourse every engineer takes in undergrad. I'm amazed at how many civil and structural engineers out there are ignorant of this concept. Makes you feel safe that they are writing the specs to build the buildings we live and work in, huh?