Originally Posted by
ajGoes
I imagine Frontier ended up with F9 because all the more plausible
two-letter codes beginning with F were already taken. The list I linked to does not include FT, though, which seems like it would fit.
FT is not currently in use, but it was used by Siem Reap Airways. The original Frontier airLines used FL, but when they returned after a long slumber, FL was taken by Air Tran (hq in FLorida) which now belongs to WN.
Oops getting a bit OT.
Oh BTW, the link to FlyerTalk's very own glossary is at the bottom of the page. All the secret codes.