The letter a fare basis code begins with, ie T03XJN5, is almost always the fare class it books into. There are very few exceptions such as DL's "UP" fares. I posted all of AS's codes here before. I'll post a link in this thread if I can get the search feature to work correctly and can find it!
I found the thread!
Here's what was posted in case you don't like clicking on hyper-links. I've made some edits to reflect the "new & improved" 3-tier coach award levels as well:
Originally Posted by
COpltASgldPHX
First Class:
F - Paid F/C and Full Flex F Awards
A - Super Saver F awards
U - All Upgrades (MVPG, MVP, Certs, Miles & Paid)
Coach:
Y - Full Flex coach fare - unrestricted/refundable AND Full Flex coach awards
S - Paid F or award F, no F cabin available*
B,M,H - "Value" coach fares
Q,L,V,K - "Bargain" coach fares, V class used for Choice coach awards & BTTs#
G,T - "Hot Deal" coach fares
W - Super Saver coach awards
* I have only seen "S" used on QX segments when I have purchased F fares. ex. PHXSEA F SEAGEG S
#Since the introduction of the three-tiered coach award system I believe V class is no longer used for revenue fares (calling Missy!) and any remaining "old school" BTTs will continue to be booked into V as well.