Basically, it is the same thing that just happened to United on their 4 miles for a HKG
ticket. The DOT (
"A purchase occurs when the full amount agreed upon has been paid by the consumer. Therefore, if a consumer purchases a fare and that consumer receives confirmation (such as a confirmation email and/or the purchase appears on their credit card statement or online account summary) of their purchase, then the seller of air transportation cannot increase the price of that air transportation to that consumer, even when the fare is a 'mistake.'"
[Edited 2012-08-08 10:50:02]