Originally Posted by
roknroll
The biggest differences in fares have to do with upgradeability, MQM earning, and refundability. Delta.com is really the best source for upgrade rules on fares, MQM earnings, etc. but you might have to do some searching to get to the right page.
I recently had the same issue as the OP, and I finally gave up searching for the answer on Delta.com.
If anyone has a link to the page on Delta.com where this information resides, please provide it. The table in the link posted above does not have all the needed information (advance purchase, restrictions, etc.).