Decreasing Airline Delay Propagation by Re-allocating Scheduled Slack

Abstract

Passenger airline delays have received increasing attention over the past several years as airspace congestion, severe weather, mechanical problems, and other sources cause substantial disruptions to a planned flight schedule. Adding to this challenge is the fact that each flight delay can propagate to disrupt subsequent downstream flights that await the delayed flights' aircraft and crew. This potential for delays to propagate is exacerbated by a fundamental conflict: slack in the planned schedule is often viewed as undesirable, as it implies missed opportunities to utilize costly perishable resources, whereas slack is critical in operations as a means for absorbing disruption. In this paper, we show how delay propagation can be reduced by redistributing existing slack in the planning process, making minor modifications to the flight schedule while leaving the original fleeting and crew scheduling decisions unchanged. We present computational results based on data from a major U.S. carrier, showing that significant improvements in operational performance can be achieved without increasing planned costs.