The US DoT DB1B Market source contains directional market characteristics of each domestic itinerary of the Origin and Destination Survey, such as the reporting carrier, origin and destination airport, prorated market fare, number of market coupons, market miles flown, and carrier change indicators. Given the number of passengers and flights, you can imagine the sheer size of the annual datasets.
We created a model to help unpack this data and generate some useful insight. Here is one page from our model that provides some key metrics.
The bold row at the bottom of each table acts as an average for the year (excluding passengers).  Look for patterns – how has mileage changed compared to fares? i.e. Spirit Airlines has seen mileage rise slightly but fares are dropping. But note their traffic has grown significantly (+33.9% between 2016 and 2018).
Subscribers can view the model here.
