A force-directed network diagram visualizes flight routes among seven cities, with node size reflecting degree centrality and color mapping to geographic region. The visualization uses D3 v7's `forceSimulation` with `forceLink`, `forceManyBody`, `forceCenter`, and `forceCollide` to position nodes, while SVG circles, lines, and text labels render the graph. Interactive drag behavior is implemented via D3's `drag` function, and a legend identifies the four region categories. The data originates from a hardcoded JavaScript array of city nodes and weighted route links.