Creative Speculation

Gravity causes the mass of the WTC to accelerate. You can (if you can do physics) do a simple momentum model and find the WTC accelerates as the mass above the impact zone falls on the lower floor, the floor fails instantly, then that mass does the same to the next floor. A WTC floor can only hold 29,000,000 pounds, about 11 floors. If as little as 6 floors fail and fall in motion, this will cause a WTC floor to collapse. If you place 12 floors of mass on a WTC floor, it will fail. Simple physics.
The WTC towers are systems. A core, a shell and floors. The core holds half or more of the gravity loads of the WTC tower, and the Shell holds half of the gravity load. The shell is the lateral support to keep the WTC from falling over in winds, in hurricane winds. The floors hold the core to the shell. Without the shell and floors the core can't stand.

Planes can fly at high speed low to the ground, someone is spreading a lie. The engines sounds were loud, yet today engines are 90 to 95 percent more quiet than engines in the 60s.

There where no explosions in the basement, because explosions turn you brain to mush - so if you are in a basement and you hear an explosion in the basement, it is the last thing you will hear, and you will not be a witness, you will be dead. The sounds in the basement were aircraft impacts as sound moves fast in steel (look it up). Illusions and ignorance drive the 911 truth lies machine of woo, and the explosions are lies, quote mined from witness statements. But go ahead, who said so, name the fire fighter.

You are ignoring science and adopting lies.

Planes going 590 mph have the energy of a 2,000 pound bomb. Where is your science? Do you want that in joules, do you do science, or repeat lies for 911 truth.

Wrong about the airplane not entering the shell of the WTC. If you check with the chief structural engineer, or an engineering school, the can explain the towers can stop an aircraft going 180 mph to 250 mph, but Flight 11 was at 470 mph, and Flight 175 was 590 mph. Thus the aircraft break into the WTC towers. Simple physics, an engineer could explain this, oops, an engineer just did. IF the WTC shell was thicker, it could stop faster planes. The WTC tower shell was very strong since it holds half the WTC weight and keeps wind from blowing over the towers.

... take a physics course quick, and don't listen to anyone in 911 truth, or anyone. Do the research.

But in a fantasy world, remember, you are safe, even small planes can't enter your building...
http://en.wikipedia.org/wiki/2002_Tampa_plane_crash