Originally Posted by
WineCountryUA
it's 24 hours just like OLCI (you can not check in luggage @ T-24 and you will not be able to clear security, but those are different issues).
Even T-24 isn't a hard and fast rule. Ticket agents have been known to check in even before T-24. It doesn't work every time, but if you've got free time on arrival and the lines are short, it may be worth asking.