From Expertflyer:

A DL FIRST CLASS
AN DL FIRST CLASS
B DL COACH
BN DL ECONOMY
C DL BUSINESS CLASS
CN DL BUSINESS
D DL BUSINESS CLASS
DN DL DELUXE NIGHT
E DL Coach - Promotional Award
F DL FIRST CLASS
FN DL DELUXE NIGHT
G DL First - Domestic PMU upgrade
H DL COACH
HN DL ECONOMY
I DL BUSINESS
J DL BUSINESS
K DL COACH
KN DL ECONOMY
L DL COACH
M DL COACH
N DL Coach - Award
O DL Business Elite - Award
P DL FIRST CLASS
Q DL COACH
R DL First - Domestic Award
S DL COACH
T DL ECONOMY
U DL ECONOMY
V DL First - Domestic segment upgrade
W DL PREM ECONOMY CLASS
X DL Business - Domestic segment upgrade
Y DL COACH
YN DL ECONOMY
Z DL Business Elite - Upgrade with PMU or points