チェックインはフライト出発のどのくらい前にすればよいですか？
We recommend that you check-in for your international flight no later than three hours before the departure time shown on your E-ticket confirmation. If you also have a domestic flight, the recommended check-in time is one hour before the departure time shown on the domestic ticket. Please note that departure times are subject to timetable changes and you should check your airline tickets for the most up-to-date information.
You will have to present your airline E-ticket, passport, and luggage to the airline staff at check-in and you will also be required to show your valid passport to an Immigration Officer.
For those guests with connecting flights within the USA, you will need to clear immigration and re-check-in your luggage at the first port of entry into the USA. The cabin crew on your transatlantic flight will give you more information on how to do this.