entrada

I have a question for those who have received a confirmed same day standby when used on line check in. The United policies make it seem that this is possible if you are within three hours of your requested standby flight. But I tried this yesterday. And although I was given the option using on-line check-in to standby for a different flight, there was no option to confirm the seat. I was given the standard depart management card for the standby flight and a boarding pass for my original flight. There were seats available on the flight I wanted to stand by for. Did I do this wrong? I didn't want to call in and once I got to the airport it cleared easily. But I was just curious why I couldn't do this at check-in on line.