How to check in right at the train station.

If you arrive by rail at the long-distance train station in the
AIRail Terminal, you can take advantage of a special check-in
service after just a few steps. Right in the passage leading from
the station to Terminal 1 is a "Check-in T" counter ("T" stands for train).
Many airlines let you conveniently check in there up to 45 minutes
prior to your flight's departure time.