Originally Posted by
DLade737
sorry what is SDFC?
A term some other carrier might use, UA's term is SDC -- "Same Day Change"
The reason once-a-day flights is a problem is the new and alternative flight must be within the same 24 hour window to make the change but if you have not board your original flight 15-30 minutes before that point is reach for once-a-day flights, your ticket will be cancelled, The practical limit is 23 hours or less for SDC.