stadium, this is where it started. I remember it being a big topic my first semester at BYU (Fall 2002). The Daily Universe did a writeup on the history. People sent letters to the editor saying they saw people get hit in the face with flying tortillas and requiring stitches as a result. Physics grad students set in a rebuttal letter summarizing the findings of lab tests showing that tortillas could not lacerate human skin.
I remember hearing about the tortillas before I moved to Provo. I still remember the beautiful sight after the first touchdown against Syracuse seeing the air above the student section fill with tortillas.