This is the list I gleaned from another forum (FT):
Fare classes
A- Discounted First (aka A4COACH class)
B- Unrestricted Economy
C- Discounted Business
D- Star Alliance Round the World (RTW) Fare - eff 1/2004 OR Restricted Envoy
E- Upgraded First from Discounted Coach (non-transatlantic)
F- Full Fare First
G- Upgraded First from Discounted Coach (non-transatlantic) - phased out in favor of E
H- Discounted Coach
I- Nonrev Envoy Class Transatlantic
J- Full Fare Business
K- Discounted Coach
L- Discounted Coach
M- Discounted Coach
N- Discounted Coach
O- Nonrev Domestic First
P- Upgraded First from Full Fare Y/B Coach
Q- Discounted Coach
R- Envoy Class Transatlantic Upgrade
S- Discounted Coach
T- Discounted Coach
Y- Full Fare Economy
U- Shuttle Coach (unrestricted)/Premium Economy Class Award
V- Discounted Coach
W- Discounted Coach
X- Domestic Economy Class Award or Nonrev
Z- Restricted Envoy
Y, B, U, and N are full-fare coach
Y, B, N, U, M, H, K, Q, V, L, W, S, T is the order from highest to lowest for coach