I don't understand that either. The typical excuse for not holding flights is that they don't want to delay down-line flights and cause further delays in the system... but UA sends 2 747's to SYD at about the same time and only 1 is needed to continue on to MEL.. so why not hold it a few minutes or an hour (to get the bags transferred) for that many pax??? Absolutely ridiculous. Is there a short time frame because of crew legality issues on such a long flight? I wouldn't think so because of the multiple flight crews on board.