UA also offers day-of buy-ups on just about every route - domestic and int'l.

Trick is they don't offer it EVERY time, so if you want a good seat, you still need to pay for it to be sure.

It's nice, however, to have the buy-up option to first on int'l flights.

I wouldn't be at all surprised if they sold half-dozen or more on most flights at about $600-700 per piece. Not a ton of money, but it does help.