Northwest Airlines  
Fare Domestic International
Description
 
A First Class Award NA Award First. Also used for plat/gold elite upgrades from domestic coach award tickets.
 
B Yes Yes Slightly full fare domestic and transoceanic
C NA Business Fare Discounted Business
D NA  Business Award Business Award
F First Class NA Discounted First
H Yes No Discounted Economy
I NA Business Upgrade This is used only for mileage upgrades from B fares
J NA Business Upgrade Full fare Business
K No   No  Deeply discounted Economy
L Yes No Deeply discounted Economy
M Yes Yes Discounted Economy. *”M” is not eligible for upgrading for travel to/from HKG, PEK, PVG or across the Atlantic.
P First Class NA Full fare first
Q Yes No Discounted Economy
R First Upgrade NA Domestic first class upgrade inventory for elite and mileage upgrades.
T No   No  Deeply discounted Economy
U NA Business Upgrade World Business Class Upgrade using Platinum Elite Upgrade certificates.
V Yes No Discounted Economy
W No   No  Domestic/Transoceanic Coach award. Also used for "free ticket" vouchers given to bumpees.
Y Yes Yes Full fare domestic and transoceanic. Y fares will receive a complimentary upgrade if there is “P” availability (elite members only!); all others can be upgraded with miles (subject to availability).
Z NA Business Fare Deeply discounted business. also used for mileage upgrades from Y
 

Code Description
X Coach
X First / Business Elite
Yes Fare is Upgradeable
No Fare is NOT Upgradeable
NA Not Applicable
? Unknown

Using miles to upgrade? – use the award charts to find appropriate mileage amounts