Landside, the only side of the airport a booking can reach
Landside is the public side of an airport, before security and passport control. Every airport booking is to a room landside; nothing reaches airside.
Airports are divided by a line that passengers cross without noticing. On one side, landside, are the arrivals and departure halls, the car parks, the railway station, the hotels and everything open to the public. On the other side, airside, are the gates, the lounges and the transit areas, reached only through security and, for some flights, passport control.
Why the line matters here
A booking can only reach a room on the landside. Hotels linked to the terminal by a public walkway qualify, as do the hotels in Schiphol-Rijk and Schiphol-Oost and any room in central Amsterdam. Nothing airside does: not a lounge, not a rest pod, not a transit hotel beyond the security line. A therapist cannot pass security, and nothing is arranged in a place she cannot reach.
What that means for a connection
A passenger with a short connection who never leaves the airside area cannot book a session, however long the wait. A passenger with a long connection who clears passport control, where required, and checks into a landside hotel can. Whether leaving the airside area is possible depends on the passport you hold and where you are travelling to and from, and it is worth checking before the flight rather than at the gate.
Arriving at night
For a late arrival, the practical point is simpler. Once you have cleared the arrivals hall, you are landside, and the room you reach from there can receive a visit arranged with an agreed journey time. The guide on Schiphol after midnight walks through the stages between the aircraft door and that room.
Leaving at dawn
On the night before a dawn departure, the session takes place in a landside room, and it closes well before you cross into the airside area the next morning. Nothing about the booking follows you past security.