I am Catholic. I have never seen this come up in any of the Catholic media (print or electronic) that I read. For a while, we were getting unsolicited deliveries of a very, very conservative (I would say reactionary) Catholic newspaper which seems to want to revoke Vatican II, but even they said nothing about "suicides" in connection with 9/11. Just now, I tried doing a google search, and nothing came up about this question as a theological issue.
Nowadays, Catholics who commit suicide do get a Catholic funeral.
But even if we go back to pre-Vatican II "conservative orthodox" thinking about this, one of the conditions that must be met for someone to be guilty of "mortal sin" is that the person makes a reasoned, free choice to do so. I hardly think running from flames while in a panic is a situation in which anyone is making reasoned conscious choices about anything.
I am pretty sure this was a nonissue.
