Maybe my memories are fuzzy but I seem to recall that, for a long time now, most global airlines (e.g. United) have been capable of allowing passengers to switch to an earlier flight if there's room, as long as the gate hasn't closed yet.

That hasn't been my experience over the past 5-6 years with Air NZ -- have they ever supported this kind of flexibility? Doesn't it seem like they should be able to? I'm often told by agents that they don't have the IT systems in place to move passengers easily at the last minute.

A few times I've tried to see if I can change to an earlier flight at the gate, never been successful. Has anyone had the experience of Air NZ supporting such flexibility?