If they say they need you 3 hours before, that means that they need a bit less time to process everybody, say 2.5 hours.<p>Now, the only thing they need is that the queue doesn&#x27;t run dry during those 2.5 hours. That means half the passengers can arrive 1 hour 15 minutes later, one in five about 2 hours later. If you are one of them, you help those coming early in the sense that they are less likely to have to waste time waiting in the check-in queues than in the slightly less annoying areas behind it (and of course, the early-comers help you to spend that hour in even less annoying circumstances)<p>And of course, assuming they have the capacity to process all passengers leaving every day, large airports could parallelize processing over multiple check-in queues, get processing time down to 30 minutes or so (using 6 check-in queues and a smart way to distribute load across them), and ask you to be there 60 minutes before departure.<p>I do not really see why they do not do that. There used to be a problem getting luggage on board the right plane, but with modern luggage processing, all bags end up on the same conveyer belt, anyways.