In alt.games.video.sony-playstation2 Mils Michael <mickmils@tiscali.fr> wrote:

> I have read from a magazine interview. People thought you could ressurect
> Aeris because she has some dialog lines after the point she's dead.
> But the truth is actually elsewhere : killing Aeris was a decision that
> was taken sometimes during the game devlopment so that they
> could have more Tifa stuff. As simple as that. They probably
> didn't bother to remove that dialog.

I thought you could use a GameShark to obtain Aeris' "ultimate weapon", 
indicating that she was originally going to be around for the whole game.

Now, whether this implies she was going to die and be re-incarnated, or 
that she was never going to die, remains a question.