The chart keeps only routes with enough sampled tickets. Among them, more airlines go with higher fares per mile in most distance bands; only distance is held fixed, so this cannot be read as the effect of competition.
What this shows: The chart plots Monopoly, Duopoly and 3+ carriers on a vertical axis of Fare per mile ($).
Conditions and method
Status: descriptive (a pattern in the data, not a causal estimate).
In 2024 Q3, routes with one carrier average 603 sampled passengers a route against 1,157 on routes with three or more carriers. The comparison holds the distance band fixed and nothing else. It does not hold fixed how busy a route is, which airlines fly it or how many of its passengers connect, and it covers one quarter.
Each bar is the passenger-weighted mean fare per mile of the routes in one distance band and one carrier-count group. A route is a directional airport pair in the DB1B ticket sample, connecting itineraries included, with at least 100 sampled passengers in the quarter; a route with one carrier is one on which a single airline sold all the sampled tickets, not a legal monopoly.