FewMiles site has them listed this way (originally taken from AA..)

Y, B, C, G, H, K, L, M, N, Q, S, V, W

[C is no longer coach].

The current AA website has them as -

Full fare Y, B
Discount H, K, M, L, W, and V
Deep Discount G, Q, N and S.

I guess whatever you do, don't buy an O fare!