Airline crew scheduling from planning to operations

doi:10.1016/j.ejor.2005.12.046

European Journal of Operational Research

Volume 183, Issue 3, 16 December 2007, Pages 1013-1027

https://doi.org/10.1016/j.ejor.2005.12.046 Get rights and content

Abstract

Crew scheduling problems at the planning level are typically solved in two steps: first, creating working patterns, and then assigning these to individual crew. The first step is solved with a set covering model, and the second with a set-partitioning model. At the operational level, the (re) planning period is considerably smaller than during the strategic planning phase. We integrate both models to solve time critical crew recovery problems arising on the day of operations. We describe how pairing construction and pairing assignment are done in a single step, and provide solution techniques based on simple tree search and more sophisticated column generation and shortest-path algorithms.

Section snippets

Background

The airline industry has been a rich source of operations research problems, mainly due to the combinatorial nature of the problems. Typically the planning problem involves creating lines of work referred to as rosters for aircraft and crew. The crew rosters consist of activities that can be flying, ground duties, training, free days, and personal activities. The crew planning process usually decomposes into two processes.

In the first process, known as pairing, the (anonymous) flying activities

The pairing problem

The pairing problem deals with the construction of itineraries consisting of flights such that all flights of a given schedule are completely covered. A flight is completely covered when all of its basic crew resource requirements are met with sufficiently many qualified crew members. A basic flight requirement is modeled with a crew-need vector of the kind [F1/F2/F3//C1/C2/C3/…], where // are used for separating the main categories of cockpit and cabin, and a single / for separating the number

The crew recovery problem

Crew recovery is time critical re-planning subject to minimal change, both in the pairing and in the rostering sense, as a result of a disruption occurring at any of the three levels. Given these disruptions, the objective here is to repair all illegal individual rosters and cover all existing or newly scheduled flights. For example,

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a flight delay makes it impossible for crew to make their connecting flight on their scheduled pairing;
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a flight cancellation due to aircraft unavailability causes

Results

We show results on instances for single base and multi-base problems where both generation methods were tested for a single recovery time window of 48 hours, within which all disruptions are considered, outside which rosters are kept locked. On all instances, the enumeration approach was always launched on the crew dependent network. It was implemented as a depth-first search (DFS) that was subject to search width parameters that limit the scope difference of the generated rosters with respect

Conclusions and further areas of research

The restrictive time limits imposed on roster maintenance and day of operation necessitates an alternative integrated approach for crew recovery. The crew recovery model (IP3) provides a framework for individualized feasible pairing generation, with additional flight or trip qualification constraints that model requirements imposed on groups of crew contributing directly in dictating pairing feasibility. When (IP3) is embedded within a sweeping time window that sweeps across a planning horizon,

Acknowledgements

The EU funded Descartes Integrated Operations Control project (together with British Airways and the Technical University of Denmark) and the Carmen Roster Maintenance project (in close collaboration with clients) initiated the research. Our special thanks go to Curt Hjorring and Lennart Bengtsson for their support and advice about the pairing reduced cost column generator. We thank Stefan Karisch for reviewing an earlier version of this work and giving useful suggestions, and Erik Andersson

References (12)

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¹: Previously with Carmen Systems AB, Odinsgatan 9, Gothenburg 411 03, Sweden.

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