Originally Posted by
ijgordon
Without the fee people would be more likely to book the cheaper flight that departs at an odd hour and then try to SDC to a more desirable one. That causes revenue leakage, probably more than the scenario you outline. If anything, standby could be free, but SDC as much 24 hours in advance is too generous (for non-elites!).
Possibly, however you can still do that today.
Given the high load factors across the industry and UA and DL allow this AND manage to get yield premiums over AA, I'm not convinced that this is that big of an issue.