To Gail's comment about Basic Economy.. I was curious because Delta has changed their policy on this several times. In checking their website, they have varying policies depending on where flight originates, and they sure make it confusing / hard to find clear info. But I finally found this:
"Basic Economy tickets cannot be changed in most cases. However, you may cancel a Basic Economy ticket issued for travel originating in the United States or Canada for travel to the Caribbean, Central America and Mexico for a cancellation charge of $99, which is deducted from the value of your ticket. For Basic Economy travel originating in the United States or Canada to any other international destination, the cancellation charge is $199."
To Tom's comment above (now removed), looks like that rule has changed since his experience. Delta website now says "For travel originating in Europe for Main Cabin and above tickets, there are no change and cancel fees. For Basic Economy tickets, the cancellation charge and change fee is €200."
I guess the bottom line is - read the fine print when buying; policies can and do change and unfortunately can be quite confusing. And of course, you always have 24 hours to cancel and get a full refund regardless of fare class. Enjoy your travels!