Join Date: Oct 2011
Location: Anywhere I need to be.
Programs: OW Emerald, *A Gold, NEXUS, GE, ABTC/APEC, South Korea SES, eIACS, PP, Hyatt Diamond
Posts: 16,046
Depending on the fare purchased. I have about a 90% confidence rate in the following.
Y for AC Y
B for AC B
M for M and under (though in the past I have seen interline with L)
I for Z and above.
If on AC (R) then it's based on the original (S+) fare class purchased.
You should be able to view the AC flight booking class by calling AC.