Originally Posted by
xliioper
It's not a "change window", it's a no-penalty cancellation window. There's no guarantee that the bucket inventory you originally booked will still be there on all the flights or that it will be preserved if you want to go back and change flights.
The 24-hour window is actually a legally mandated window where you're allowed to change or cancel your flight at no charge - that's why all the airlines offer it, at least in the US (not sure about outside the country). They enacted that at the same time that it became mandatory to include all fees in the displayed price. And when you click through to change or cancel your delta flight within this window on the website, you can select one or both parts of a round trip to change or cancel - since I selected only the departure, that's why I thought it was weird that the return changed.
The cost difference wasn't actually $200, sorry for the confusion - it was a bit less than that, and was clearly labeled as the fare difference between my original departure and the modified departure (and was not indicated as part of a chance to the return).
Regardless, not a big deal, but I figured that if anyone else is working on a partial change to a trip they should keep an eye on the other flights involved to make sure nothing strange happens.
Thanks!