<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by GG:
RRWhite: U fares are absolutely non-upgradeable. L fares can only be upgraded with old Frequent Flier miles. Of course operational upgrades are a thing unto themselves.
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On a couple of occasions I have been able to use segment upgrades with an L fare. On one of those, the agent volunteered the upgrade at check in. These were not operational upgrades as coach had open seats. Luck of the draw I guess.