Equitable Optimization of U.S. Airline Route Networks

TL;DR

This paper presents an open-source framework for restructuring U.S. airline routes to reduce emissions and improve accessibility, balancing environmental impact with community connectivity.

Contribution

It introduces a novel metric for airport accessibility, combines it with emissions estimation, and develops an optimization model for route network redesign.

Findings

25% reduction in total flights

4.4% decrease in emissions per seat-mile

17.6% improvement in accessibility distribution

Abstract

Restructuring route networks (i.e., modifying the graph of origin-destination pairs) remains a promising alternative for reducing the airline industry's environmental impact. However, there exists a fundamental trade-off between emissions from flight and airport accessibility, since flights connecting underserved, low-accessibility communities tend to possess high CO2 per seat-mile ratios. Thus, this work develops an open-source analytical framework and methodology that restructures U.S. airline route networks to simultaneously minimize emissions and maximize airport accessibility. To achieve this goal, this paper designs a metric to quantify airport accessibility and combines it with an open-source system-wide emissions estimation methodology. This facilitates the creation of a mixed-integer linear optimization model that returns revised flight frequencies and aircraft allotment. Using United Airlines 2019 Q3 data as a case study, this model is able to construct an alternative route network with a 25% reduction on the total number of flights, 4.4% decrease in the average emissions per seat-mile and a 17.6% improvement in the spread of the airports' accessibility scores, all while satisfying historic passenger demand.