I think this problem is particularly an issue with UX flights. I have no problem with moving a departure time back up if a plane is found etc. but the *communications* to the customer most definitely is an issue. Even if a customer is sitting is a club there is literally no way that a moved up departure time can keep such a person from getting to the gate (at any airport I know of) if the change is communicated when the new aircraft is identified. The airline has to know at least 20 (and really more like 30) minutes ahead of departure of the new plan - it takes that long to get the dispatch in order and get loaded bags and boarded even in the best of cases. What I have seen for years though (with particular volume of cases at PDX) is that the UX operators are very bad at updating the info systems that UA has talking to passengers. That is why you see things like a GA thinking the flight is still delayed. Club agents often know this and I have had many of them roll their eyes at me and ask me to wait before I head to the gate while they call to get an update from the actual agent at the gate. I'm not saying that this sort of situation doesn't arise with mainline but it is much, much worse with UX. There really is no excuse for not communicating information in a timely manner via the online and terminal monitors which would avoid such events as this.