Explanations on Different Airfare Classes (e.g., L, K, Y, etc.)

Have you ever wondered what the different cabin classifications are? Such as L class versus K class? I am flying Delta today (BTW, Delta stands for Don’t Even Leave The Airport) and they are not able to upgrade me because my ticket was issued as a L class. So I decided to look it up:

A – First Class Discounted
B – Coach Class Discounted
Bn- Night Coach Discounted
C – Business Class
Cn- Night Business Coach
D – Business Class Discounted
E – Shuttle Service
F – First Class
Fn- Night Coach in First Class Compartment
H – Coach Class
J – Business Class Premium
K – Coach Class Discounted
Kn- Night Coach Discounted
L – Coach Discounted
M – Coach Discounted
N – Coach Discounted
P – First Class Premium
Q – Coach Discounted
Qn- Night Coach Discounted
R – Supersonic
S – Coach
T – Coach Discounted
U – Shuttle Service
V – Coach Discounted
Vn- Night Coach
W – Coach Premium
Y – Coach
Yn- Night Coach
Z – Business Class Discounted