Originally Posted by
xliioper
If you are changing flights before departure of outbound, fares generally require using current fares and measuring advance purchase from the current date and you will pay any fare difference between what you paid and what is currently showing on flights.
It depends upon the fare, but many (most?) UA fares allow you to change the return if the outbound is not affected, even prior to the date of travel. I think somebody finally realized that it was silly to charge someone the walk-up fare if they made a (return) flight change the morning of their outbound, or potentially $0 if they made the same change the next morning.
You'll see it in the fare rules, something like this:
Code:
BEFORE DEPARTURE
...REPRICE USING CURRENTLY TICKETED/HISTORICAL FARE
PROVIDED ALL OF THE FOLLOWING CONDITIONS ARE MET -
--
1. NO CHANGE 1ST FLIGHT COUPON / NO CHANGE TO
FARE BREAKS
There will be more conditions than just the first one, but when you look at them in total, you'll generally find that they cover most situations.