[varispeed]

I heard horror stories, where "secure storage area" was actually a field without any security. Not saying this is the case here, but one must be mad to give a car like that without knowing exact location it is going.

It's one of the things where I can't see what is there robot's role here.

[djhworld]

I doubt the robots have sufficient enough traction/mobility to navigate on any surface that isn't reasonably smooth like tarmac. Also I'd wager the car park the robots go to isn't that far away from the drop off location, most likely on the same land owned by the airport.

[varispeed]

My guess is they take the car away from the drop off point to employee pick up point and human drives them away to the "secure location".