21Schedule Robustness

21.1 Introduction

The main objective of the airline planning process is to develop the future flight schedule as well as the schedule of all resources (aircraft, gates, crew, ground staff, etc.) used to operate all scheduled flights. Airlines spend significant effort to develop an optimal schedule for flights and resources in order to maximize its net revenue. However, during the operation phase, the scheduled flights and resources could be subject to several sources of unexpected disruptions. These disruption sources include, for example, adverse weather conditions, aircraft breakdown, unexpected air traffic congestion, and sometimes computer system glitches. These disruptions could result in a reduced system capacity or purging resources needed to operate the flights. Thus, they lead to undesired flight delays and cancellations that jeopardize the optimality of the originally planned schedules.

Disruption scenarios vary by source, location, severity, impact, and recoverability. Large‐scale airline operating hundreds of daily flights is encountering these disruptions on a daily basis. In the United States, for example, the average on‐time performance rate for scheduled flights is in the lower 70%. The on‐time performance rate measures the percentage of flights that arrive at its destination within 15 minutes from its scheduled arrival time. This measure indicates that only three flights out of each four flights operate as planned. Such low on‐time arrival ...

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