I can make a flight change with NO fees, except I must pay to reflect the difference in fares--what base is DL using? The price for my flight vs. the price for the flight I want to change to on the change dateor the price I paid when I purchased my ticket vs. the price I want to change to on the change date.
If my flight is part of a DL Vacation package how do they know how much I paid?
PS: I want to change from a d1 later to a d1 earlier on the same day.