Reply #14: What I've never figured out is

[mirandapriestly]

whether a material like aluminum can break through steel. I've asked before and OCTers have assured me that it makes no difference , the only thing that matters is the velocity, but I don't know about that. Why aren't bullets made out of aluminum, then? The engines are the only thing that seem heavy enough to really make an impact, but the nose went through first and noses are so fragile that birds will dent them and seriously damage them. I can't imagine a plane at any speed damaging a steel building like that. Also the 2nd plane was supposedly going faster, but the damage did not look any worse. So if speed is all that matters why wouldn't the damage be worse?