The train connection together with the Lufthansa ticket can be booked online at LH.com, via mobile on the Lufthansa App or in a travel agency. Passengers can benefit from a connection and transfer guarantee as well as a mileage voucher for Miles & More. Passengers can check in for the air-rail journey online or by mobile from 23 hours up to 15 minutes prior to the scheduled departure of the train and automatically receive all boarding passes for the trip, which are simultaneously valid as a train ticket.
Lufthansa passengers may also hand in their luggage directly upon arrival in the AiRail Terminal at Frankfurt airport. This is located in the passage between the railway station and Terminal 1 of the airport. Passengers who are only travelling with hand luggage may proceed directly to their departure gate. Passengers in Business Class, HON Circle Members and Senators may use the DB-Lounge at the railway station of Frankfurt airport.
Lufthansa has now been offering this intermodal service with partners Deutsche Bahn and Fraport for 15 years. In 2001 the first Lufthansa AIRail route was created with Stuttgart. In recent years this has been continually expanded under the new brand name ‘Lufthansa Express Rail’ to include the present five cities within Germany: Cologne, Dusseldorf, Karlsruhe, Mannheim and most recently Dortmund.
Every year around 300,000 Lufthansa passengers use this offer on one of the 25,000 connections.
Cited from http://airportfocusinternational.com