Transparency (opacity) of vertices in Pajek

Opacity property specifies the transparency of vertices, that is, the degree to which the background behind the vertices is overlaid. Drawing transparent vertices when layout is exported to SVG is available in Pajek (4.09 or higher).
Picture shows network of airline connections among US airports. Size of an airport is proportional to its Laplacean centrality. Edges were excluded from the layout for the sake of clarity. Touch the vertex to display the airport's name.