Originally Posted by
sethb
How do you know it doesn't increase your chances of upgrading? It's a different fare class, and upgrade goes by fare class.
W is the booking fare class, but you're still paying for an underlying fare class. When you read the booking class it will be WL, WM, etc. The second letter is the class of the fare you're paying. They then combine it and whatever amount the choose for the C+ product and book you into WX. This allows them to limit the number of seats in C+ given out to each fare. Your upgrade to first will be based on the fare class paid, ie the second letter of the WX combination.