Figure 1. Visual representation of the ATN.

From left to right: the aggregate network of all the layers in which only links belonging to more than one layer are displayed. The same network but in which we display those links which belongs to only one layer and connecting at least one node with degree greater than or equal to 75. An example of ATN network of a major airline and, finally, the network of a low-fare (low-cost) airline. In each network, the airports with the highest degree are highlighted.