Old Oct 17, 19, 1:51 pm
Join Date: May 2015
Location: Vancouver
Programs: Aeroplan, Mileage Plus, WestJet Gold, AMEX Plat
Posts: 1,947
Originally Posted by garykung View Post
Because it is an upgrade. In airlines perspective, allowing to upgrade (i.e. not upfare) is a favour to you, as you would be able to enjoy premium class with a discount.

Airlines prefer you actually buy into discounted premium instead.
That could be the real reason. More likely the reason is the IT systems does talk to each other in the correct places to make this happen.
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