Sentence:  One of the requirements in <WSD>Schengen</WSD>, quite practically, is that you have configure airports so that you can separate out your air travellers from those who are travelling within <WSD>Schengen</WSD> and those who are not. 
Meaning of the word marked with <WSD> tags:  The Schengen Area; the area over which the Schengen Agreement applies.