<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by svpii:
I know that recently on my CLT_LGW leg when I had left the transatlantic upgrade certs on my desk at home (*gasp*), the agent first asked if I would like to upgrade w/ miles - until he noticed I was booked in K class, which couldn't be upgraded w/ miles.. so I think you can, but it's risky... if you're prepared to do that, why not go ahead and do it now? Hoping for an operational upgrade? 
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Fortunately, now you can upgrade that K class ticket with miles. Excellent change for Dividend miles.
One-Way Upgrade Awards
One-way upgrades are available within North America and between North America and Europe.
US Airways One-Class Upgrades
Unrestricted Fare
Restricted Fare
MILEAGE LEVEL
AWARD CODE
MILEAGE LEVEL
AWARD CODE
One-way between North America1 and Europe
10,000
(J, C, Y or B class fares)
USE1
20,000
(M, H, K or Q class fares)
USE2