[SusieP.]

Spoiler:

I'm thinking that everyone on the plane willed that plane to crash. That they all, for a brief second, had the thought that the only way out of their situation was to die and their collective thoughts made the plane go down. They were all in various desperate situations, like it would be easier for Charlie just to kill himself or whatever than to get off heroin. Or for Claire, rather than having the demon baby. Or for Locke, who couldn't walk at that point. Etc, etc.

I'm gonna have to watch it again. I was not surprised when Artz blew up. While he was talking to Hurley I was thinking, I bet they introduced this guy so they could kill him off...and BOOM! He was gone.