Thanks for the info. Sorry I posted here, I wasn't sure where to post, as I'm actually curious what the general policy is, not just Delta, and couldn't find a generic enough question forum. In this specific trip, I care about Delta moving to Continental, but usually I book United, so I'd be curious moving off United onto another carrier.

So, it sounds like there's not much I can do without a mechanical/weather issue. Strange, I've heard this happens a lot just going earlier (maybe the original flight was overbooked).

Thanks again!