Originally Posted by
mfkne
BHX has a free (albeit short) shuttle train, there's the shuttle bus at FRA that goes between terminals (and the train station), which is free of charge too. There's more examples than just the one. DLR at LCY is a bad example since LCY is just a stop along a regular light rail line - SkyTrain just goes back and forth between the airport and the train station.
Thatīs different in my eyes. Transportation between terminals is more or less always free, also in CDG, STN, LHW and so on. Skytrain is from an extern point (train station) to the airport.