Obviously it stems from the superstition of it (lots of hotels still don't have a 13th floor), but I'm not certain where it originated at AirTran.
It was definitely an old Eastern thing (the only concourse in ATL
that didn't have a gate "13" is C - the old Eastern concourse), so I wonder if because so many of ValuJet's original managment (not the 4 who started the thing, but the flight ops people who really got the operation going) were ex-EA people I wonder if that's where it came from.
I'm also thinking maybe the ex-DL DC9s they started with came without row 13s, and so the tradition was just continued. One other possible excuse was that in the original ex-DL ValuJet config, the exit rows were 14, 15, and 16, so by NOT changing them, the first exit row would have been 13, and maybe
that was the reason.
Who knows, but for which ever reason, it was begun in the early days of ValuJet and just continued on....