I'll be travelling ORD-PRG in August, and I'm trying to figure out if an upgrade will be at all feasible, or if I should just go ahead and book premium economy with cash (I don't have a lot of miles and it's questionable if I'd get the 50k required for the upgrade in time anyway).

The fine print under the upgrade award chart says this: "Upgrading from Economy Class to Business Class or First Class results in additional premium cabin taxes and carrier-imposed fees, including but not limited to flights originating in Great Britain and France."

Are Great Britain and France special, or will I have to pay the difference in carrier-imposed fees regardless of where I connect? Can I calculate what that will cost by taking the difference of the copays for an award ticket (example in the screenshot $1577 - $587 = $990)? If so, unless there are any tricks I haven't considered, I'll stop worrying about the upgrade and probably just book premium economy.

Okay so apparently I can't post a screenshot with a new account, but hopefully I've described it well enough.