Hybrid methods for integrated aircraft routing and crew pairing problem with short flight legs

The aircraft routing and crew pairing problems are two processes that are difficult to be solved in the airline operations planning due to the rules that each flight leg needs to be operated on by one aircraft and one crew pair. These two problems, though interrelated in practice, are usually solved sequentially and often leads to suboptimal solution. Thus, this research contributes to the solution of the integrated aircraft routing and crew pairing problem in order to determine the minimum cost of this integrated problem where each flight leg is covered by one aircraft and one crew pair. This study also considers short connection between two flight legs in order to ensure that the crews do not change the aircraft if the connection time is in between 20 to 59 minutes. Another consideration is the restricted connection that imposes penalty costs when the second flight leg uses the same crew but not the same aircraft. Based on the literature review, most of the existing solutions concentrate on minimizing the planned costs. Although the minimum costs are significantly important in airline operations planning, the efficiency of a solution method in terms of computational time cannot be neglected. It is necessary to solve the integrated problem by using an efficient model that is able to generate a good high quality solution in a short time as requested by the airline industry. In order to solve the problem, a set of feasible aircraft routes and crew pairs are initially generated to be used as the input data in solving the integrated model effectively. There are two heuristic methods which are proposed in generating the set of feasible aircraft routes and crew pairs namely constructive-based heuristic and Genetic Algorithm (GA). The generated feasible aircraft routes and crew pairs are then used in solving the integrated problem by using Integer Linear Programming (ILP) method, Dantzig Wolfe Decomposition method, Benders Decomposition method and Particle Swarm. Computational results obtained from these methods are then compared by testing them on four types of aircraft with different number of flight legs based on Malaysia local flights for one week flight cycle. From the numerical results, it can be concluded that the proposed methods are more efficient compared to the ILP method available in the literature in terms of the computational time where the hybrid algorithm of GA and Benders Decomposition is found to be advantageous compared to the others. The maximum cost deviation of only 4.77% also justifies the strength of this hybrid algorithm. One possible future research that can be extended from this study would be the development of an algorithm that incorporates a parallel GA within the proposed methods for larger instances which are likely to exist in international flights in order to speed up the planning process

Χρονοδρομολόγηση Ιπτάμενου Προσωπικού Αεροπορικών Εταιριών

Σκοπός της παρούσας πτυχιακής εργασίας είναι η δημιουργία αλγορίθμου που εξετάζει και υλοποιεί την ανάθεση πληρωμάτων (crew assignment) - συνδυασμών πτήσεων (pairings) σε πιλότους - με περιορισμούς που ενεργοποιούμε εμείς σε κάθε εκτέλεση και τον έλεγχο της εγκυρότητας ενός σεναρίου αναθέσεων συνδυασμών πτήσεων σε πιλότους. Το πρόβλημα επιλύεται με την γλώσσα προγραμματισμού C++ και ενεργοποιεί τους περιορισμούς μέσω ορισμάτων από την γραμμή εντολών για να είναι εύχρηστο και φιλικό προς τον χρήστη. Τα αποτελέσματα δείχνουν ότι ο αλγόριθμος είναι σε θέση να αναθέσει αποτελεσματικά τους συνδυασμούς πτήσεων και να ελέγξει την εγκυρότητα των υπαρχουσών αναθέσεων. Αφού υλοποιηθεί η μέθοδος γίνονται προσομοιώσεις για να αξιολογηθεί τελικά η ικανότητα της μεθόδου να αναθέτει και να ελέγχει τα ταιριάσματα πτήσεων ανάλογα με τους περιορισμούς που ενεργοποιούμε, την δίκαιη ανάθεση στους πιλότους, αλλά και την ταχύτητα με την οποία το κάνει αναθέσεις. Τέλος παρουσιάζονται τα αποτελέσματα και βγαίνει ένα τελικό συμπέρασμα. Το πρόγραμμα είναι φιλικό στον χρήστη και δίνει την δυνατότητα να ενεργοποιεί όσους περιορισμούς χρειάζεται πολύ εύκολα με την χρήση ορισμάτων από την γραμμή εντολών. Σημαντικό στοιχείο είναι η υλοποίηση του αλγορίθμου με τρόπο που διευκολύνει την αλλαγή των υπαρχόντων περιορισμών και την υλοποίηση επιπλέον περιορισμών ώστε να επεκταθεί χωρίς πρόβλημα η προσομοίωση με το σκεπτικό ότι το περιβάλλον της κάθε αεροπορικής εταιρείας μπορεί να αλλάζει με δυναμικό και απρόβλεπτο τρόπο

Uma aplicação de programação inteira para otimização do planejamento da fiscalização no âmbito da Agência Nacional de Aviação Civil - ANAC

O presente trabalho tem como objetivo propor uma modelagem da alocação de fiscais da Agência Nacional de Aviação Civil - ANAC. O problema consiste em minimizar o custo de diárias e passagens dispendido no exercício da fiscalização em Centros de Instrução de Aviação Civil (CIAC). Os fiscais, que estão lotados em quatro cidades, e os CIACs, localizados em mais de 180, demandam inúmeros deslocamentos na realização das fiscalizações. Com restrições orçamentárias cada vez mais severas no âmbito do Poder Executivo Federal, vê-se a necessidade de utilizar os recursos de maneira ótima, evitando desperdícios. Para tanto, foram utilizados dados reais para modelagem e resolução do problema. A abordagem ocorreu dividindo o problema em duas etapas, uma para geração das missões de trabalho e a outra para a alocação das equipes de inspeção. Dessa forma, buscando a geração da menor quantidade de missões e, na sequência, o menor custo da alocação dos inspetores ao longo do período de doze meses. Considerando a natureza de Programação Inteira do problema, o método de Geração de Colunas foi implementado, assim como um algoritmo heurístico para resolução. Adicionalmente, foram analisadas as implicações gerenciais da utilização do modelo, incluindo simulações de cenários com diferentes parâmetros. Os resultados obtidos indicam que é possível utilizar de forma mais eficiente os recursos disponíveis na ANAC. Ademais, a divisão do problema permitiu que fosse gerado um número mínimo de missões, garantindo uma significante redução no custo de passagens aéreas. Sendo assim, foi possível desenvolver e implementar uma modelagem capaz de ser utilizada de forma estratégica no planejamento das fiscalizações programadas no âmbito da ANAC.This work aims to propose a model for inspectors assignment in the National Civil Aviation Agency - ANAC. The problem consists in minimizing the cost of daily allowance and tickets spent during inspections at Civil Aviation Instruction Centers (CIAC). Inspectors, who are based in four cities, and CIACs, located in more than 180, demand numerous trips to carry out the inspections. With budget restrictions increasingly severe within the Brazilian Federal Administration, there is a need to use resources optimally, avoiding waste. For that, real data were used to model and solve the problem. The approach took place by dividing the problem into two stages, one for the generation of work missions and the other for the assignment of inspection teams. Thus, firstly, ensuring the generation of the minimum quantity of missions and, subsequently, the lowest cost of inspectors assignment over the twelve-month period. Considering the Integer Programming nature of the problem, the Column Generation method was implemented, as well as a heuristic algorithm. Additionally, the management implications of using the model were analyzed, including simulations of scenarios with different parameters. The results obtained indicate that it is possible to use the resources available at ANAC more efficiently. Furthermore, the division of the problem allowed a minimum number of missions being generated, reducing significantly the cost of airline tickets. In this way, it was possible to develop and implement a model capable of being used strategically in the planning of inspections scheduled within the scope of ANAC

Optimisation simultanée des rotations et des blocs mensuels des équipages aériens

R´esum´e Le probl`eme int´egr´e de la construction des rotations et des blocs mensuels des pilotes consiste `a d´eterminer un ensemble de rotations et de blocs mensuels pour les pilotes tels que chaque segment de vol est couvert par une seule rotation et un seul bloc, et ce, tout en satisfaisant des contraintes suppl´ementaires comme la disponibilit´e des pilotes dans chaque base. Une rotation est une s´equence de vols effectu´ee par un ´equipage durant une p´eriode donn´ee partant et revenant `a la mˆeme base. Un bloc (ou horaire) mensuel est une s´equence de rotations s´epar´ees par des p´eriodes de repos. La construction des rotations et des blocs mensuels doit ˆetre conforme aux r`egles de la s´ecurit´e a´erienne, aux r`egles d’op´eration de la compagnie et aux r`egles contenues dans les conventions collectives entre les employ´es et la compagnie a´erienne. `A part l’introduction, la revue de litt´erature et la conclusion, cette th`ese est compos´ee de trois chapitres principaux dont chacun pr´esente les travaux r´ealis´ees pour un objectif de recherche bien pr´ecis. Ces trois chapitres utilisent les mˆemes instances du probl`eme bas´ees sur des donn´ees r´eelles fournies par une grande compagnie a´erienne am´ericaine. Le probl`eme de construction des rotations se r´esout traditionnellement en trois phases de mani`ere s´equentielle : un probl`eme journalier, un probl`eme hebdomadaire et un probl`eme mensuel. Cette approche interdit la r´ep´etition du mˆeme num´ero de vol dans une rotation. Le premier objectif de cette th`ese est de mettre en ´evidence deux faiblesses de cette approche s´equentielle et proposer `a la place une approche alternative qui permet la r´ep´etition des vols dans une mˆeme rotation. Premi`erement, nous montrons que lorsque l’horaire des vols est irr´egulier, les deux premi`eres phases ne sont qu’une perte de temps et on peut obtenir de meilleures solutions en moins de temps si le probl`eme mensuel est r´esolu directement en utilisant une approche d’horizon fuyant faisant appel `a une m´ethode de g´en´eration de colonnes. En effet, cette approche a permis de diminuer le gras de la solution de 34% en moyenne o`u le gras est une mesure de qualit´e portant sur le pourcentage du temps non travaill´e mais pay´e durant un horizon. Deuxi`emement, mˆeme si l’horaire des vols est compl`etement r´egulier, la qualit´e de la solution est meilleure si le probl`eme hebdomadaire est trait´e directement sans exploiter le probl`eme journalier. En effet, les diff´erents tests ont montr´e qu’une moyenne de 48.8% des rotations contiennent des r´ep´etitions causant une r´eduction moyenne de 16% dans le gras.----------Abstract The integrated crew pairing and crew assignment problem for pilots consists of producing a minimum-cost set of pairings and schedules such that each flight leg is covered once by one pairing and one schedule, and side constraints are satisfied such as pilot availability in each crew base station. A pairing is a sequence of duties separated by rest periods that must start and end at the same crew base. A duty is a sequence of flights separated by connections and ground waiting times, forming a working day for a crew. The construction of pairings and schedules must respect all safety and collective agreement rules. Besides the introduction, literature review and conclusion, this thesis is composed of three main chapters where each one presents the performed work for a specific research objective. These three chapters use the same problem instances based on real-data provided by a major US airline. The crew pairing problem has been traditionally solved in the industry by a heuristic three-phase approach that solves sequentially a daily, a weekly, and a monthly problem. This approach prohibits the repetition of the same flight number in a pairing. The first objective in this thesis is to highlight two weaknesses of the three-phase approach and propose an alternative solution approach that exploits flight number repetitions in pairings. First, when the flight schedule is irregular, we show that better quality solutions can be obtained in less computational times if the first two phases are skipped and the monthly problem is solved directly using a rolling horizon approach based on column generation. In fact, this approach has reduced the solution fat by 34%. The solution fat is a quality measure that shows the percentage of time not worked but paid. Second, even if the flight schedule is completely regular, we show that better quality solutions can be derived by skipping the daily problem phase and solving the weekly problem directly. Indeed, the proportion of pairings with such repetitions represents 48.8% causing a mean reduction in the solution fat by 16%. In practice, both the crew pairing and crew assignment problems are independently modeled and sequentially solved. The use of a sequential approach considerably reduces the complexity of the global problem but produces solutions that may not be conform with airline desires. The second objective in this thesis is to propose a model that fully integrates the crew pairing and crew assignment problems and solve it in a single step. Due to the large size of this integrated model, we propose a solution method that combines a column generation and a dynamic constraint aggregation method. Since the latter method requires a good initial partition, this partition is provided by a set of pairings found with the sequentia

Análise comparativa do modelo de negócio das companhias aéreas legacy vs low-cost : um estudo empírico aplicado à TAP Air Portugal e Easyjet

Orientação: José Manuel Ivo Carvalho VicenteEsta dissertação de mestrado apresenta um estudo que tem como objetivo analisar o modelo de negócio das companhias aéreas legacy e low-cost, desde as várias componentes que compõem a estrutura base das mesmas (gestão das aeronaves, tripulações, etc.), até às principais vertentes que regem o setor do transporte aéreo internacional (procura, oferta, concorrência, entre outros), aplicando como principal fonte de dados e informação, os resultados auferidos pela TAP Air Portugal e easyJet. Em termos da metodologia implementada, esta baseia-se essencialmente na aplicação de entrevistas (a dois profissionais do setor aeronáutico) e questionários (dando a conhecer a importância dada a certos fatores de escolha ao voar em determinada companhia aérea, do ponto de vista do passageiro comum), complementando a investigação com a utilização de ferramentas como o Estudo de Caso, a Análise Estatística e a Análise das Hipóteses Concorrentes. Relativamente à sua planificação, esta dissertação encontra-se delineada em oito capítulos, em que o primeiro se encontra dedicado à parte introdutória da mesma, do segundo ao quinto capítulo, é feita a revisão do estado da arte abordando tópicos relacionados com a gestão e estrutura de uma companhia aérea, a diferença entre os dois modelos de negócio abordados, a análise da regulação económica no transporte aéreo, entre outros. Os últimos três capítulos, abordam a metodologia de investigação utilizada, a análise dos dados recolhidos mediante a pesquisa implementada e as principais conclusões retiradas, respetivamente. Após a resolução do estudo, os principais resultados obtidos reiteram um possível equilíbrio (e até uma aproximação) entre os dois modelos de negócio abordados, num futuro próximo, sendo que a probabilidade de sucesso de determinada companhia aérea encontra-se bastante associada à capacidade da mesma em fornecer um serviço que possua o maior benefício em termos de qualidade vs preço, para o passageiro, mantendo os padrões de segurança o mais alto possível.This master's dissertation presents a study that aims to analyze the business model of legacy and low-cost airlines, from the various components that make up their base structure (aircraft management, crew, etc.), to the main ones governing the international air transport sector (demand, supply, competition, among others), applying as its main source of data and information, the results obtained by TAP Air Portugal and easyJet. In terms of the methodology implemented, it is based essentially on the application of interviews (to two aeronautical professionals) and questionnaires (making known the importance given to certain factors of choice in flying in a particular airline, from the passenger point of view), complementing the research with the use of tools such as Case Study, Statistical Analysis and Concurrent Hypothesis Analysis. Regarding its planning, this dissertation is delineated in eight chapters, in which the first one is devoted to the introductory part of it, from the second to the fifth chapter, a review of the state of the art covering topics related to management and structure of an airline, the difference between the two business models addressed, the analysis of economic regulation in air transport, among others. The last three chapters cover the research methodology used, the analysis of the data collected through the research implemented and the main conclusions drawn, respectively. After the resolution of the study, the main results obtained reiterate a possible balance (and even an approximation) between the two business models approached, in the near future, and the probability of success of a particular airline is closely associated with the capacity of providing a service that has the greatest benefit in terms of quality vs. price, to the passenger, while maintaining safety standards as high as possible

Modeling and Solving A Crew Assignment Problem in Air Transportation

International audienceA typical problem arising in airline crew management consists in optimally assigning the required crew members to each flight segment of a given time period, while complying with a variety of work regulations and collective agreements. This problem called the Crew Assignment Problem (CAP) is currently decomposed into two independent sub-problems which are modeled and solved sequentially: (a) the well-known Crew Pairing Problem followed by (b) the Working Schedules Construction Problem. In the first sub-problem, a set of legal minimum-cost pairings is constructed, covering all the planned flight segments. In the second sub-problem, pairings, rest periods, training periods, annual leaves, etc. are combined to form working schedules which are then assigned to crew members.In this paper, we present a new approach to the Crew Assignment Problem arising in the context of airline companies operating short and medium haul flights. Contrary to most previously published work on the subject, our approach is not based on the concept of crew-pairings, though it is capable of handling many of the constraints present in crew-pairing-based models. Moreover, contrary to crew-pairing-based approaches, one of its distinctive features is that it formulates and solves the two sub-problems (a) and (b) simultaneously for the technical crew members (pilots and officers) with specific constraints. We show how this problem can be formulated as a large scale integer linear program with a general structure combining different types of constraints and not exclusively partitioning or covering constraints as usually suggested in previous papers. We introduce then, a formulation enhancement phase where we replace a large number of binary exclusion constraints by stronger and less numerous ones: the clique constraints. Using data provided by the Tunisian airline company TunisAir, we demonstrate that thanks to this new formulation, the Crew Assignment Problem can be solved by currently available integer linear programming technology. Finally, we propose an efficient heuristic method based on a rounding strategy embedded in a partial tree search procedure.The implementation of these methods (both exact and heuristic ones) provides good solutions in reasonable computation times using CPLEX 6.0.2: guaranteed exact solutions are obtained for 60% of the test instances and solutions within 5% of the lower bound for the others