Well, I think one has to look at it case by case.
My intuition tells me that if these small regioal fields would not be there, the 2.3 mil pax would take the train to a mayor to get their flight.
It may look silly but that's how it works.
If tomorrow you open a stand at your front door selling oranges, you will start to sell.
Claiming afterwards those clients cause problems to the traffic flow is a bit like the story of the egg and the chicken.
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Smooth Trimmer