I don't know when AMEX instituted this policy, but when I tried to enter a dispute on the baggage fee issue, I got this response:



Our records indicate this transaction is associated with special services provided by the airlines, such as checked / excess / overweight baggage, advanced seat assignment or travel modifications made within 24 hours of departure. These special services were pre-purchased online or with an airline agent and are non-refundable.
Please contact the airline directly with any questions you may have or to dispute the charges. We realize this may not be the response you hoped for, but trust you will understand that we must abide by the merchant's policies.
If you wish to initiate a billing inquiry at a later date or check the status of an Open Inquiry or the details of a Closed Inquiry, please visit us online through the Inquiry & Dispute Center.
You may return to the Inquiry and Dispute Center by clicking here. Please bookmark this URL for future reference.

Looks like I might have to send snail mail to get this dispute entered into AMEX's system.