If an airline charged an amount in addition to the originally quoted price, I believe that would get reversed pretty quickly. I'm pretty sure it's against business' agreement with the credit card companies, and the card holder is not agreeing to some "unknown surcharge" when they provide their CC info. If airlines really cared about this (i.e. if it really cost them a significant amount) they would authorize an additional known amount as a "deposit" and then refund that after the last leg is flown, a la some car rentals, hotel reservations etc. But they don't, because it's not really that big of a problem on the grand scheme of things.

rb211.