Originally Posted by number_6
What I've been told is that there is a hefty fee for landing prior to 6 am; some airlines prefer to pay the fee, others will circle burning fuel. The fee must be large to warrant burning fuel for half an hour (my own experience, more than once). The airport is open and operating, it is just a noise abatement procedure; the fee varies with runway direction which in turn is determined by wind conditions; I don't know if it is CX policy to always land immediately or only when the wind is blowing in the right direction.
If there's a hefty fine, doesn't it seem odd that Cathay would actually schedule a 5AM arrival? If all that is so, aircraft utilization must be more significant than the fine, and the curfew isn't very useful to the residences it's presumably trying to keep noise-free overnight.