This multi-line chart displays monthly flight delay counts for four delay categories—carrier, late aircraft, national aviation system, and weather—across airports. It loads CSV data from a GitHub gist using `d3.csv`, then renders paths via `d3.line` with a `d3.scaleBand` x-axis and `d3.scaleLinear` y-axis. Color-coded lines and a manual legend distinguish categories, while axes are generated with `d3.axisBottom` and `d3.axisLeft`. The SVG output uses D3 v6 with the d3-legend library.