Towards the optimisation of the schedule reliability of aircraft rotations

A cost minimisation model is developed to optimise the scheduling of aircraft rotation by balancing the use of schedule time, which is designed to control flight punctuality, and delay costs. A case study is conducted using schedule and punctuality data from a European airline. Optimisation shows that the operational performance of an aircraft rotation schedule is improved in terms of: schedule regularity, mean delays and expected delays of aircraft rotation. Although the total schedule time of the study rotation is increased by 5%, a system cost saving of some $9.3 million/1000 aircraft rotations is gained after schedule optimisation. Three schedule reliability surrogates—mean delay time of aircraft rotation, expected delay time of aircraft rotation and schedule regularity—are employed to evaluate the reliability of aircraft rotation schedules. It is found that the reliability and robustness of schedule implementation is significantly improved after optimisation.     

A heuristic approach for solving an integrated gate reassignment and taxi scheduling problem

Capacity limitation of airport ground operation is one of the major limiting factors in air traffic operation. The congestion on the gate and taxiway causes severe delay and propagate effect on the flight schedule. This paper considers the problem of integrated gate reassignment and taxiway scheduling, in which complex constraints related to runway restriction, gate allocation and taxiway conflict are all incorporated when determining the schedule. To solve this problem, we propose a novel heuristic approach. First, all possible aircraft schedules are enumerated by disretizing the waiting time along the path. Then, the cost is evaluated for each schedule and the conflict detection is conducted to generate constraint sets. Finally, we propose a set partition model, in which each decision variable denotes a candidate schedule that takes into account the possible constraints when generated. This method is compared with a sequential method that solves gate reassignment and taxiway scheduling problem separately. Computational results highlight the strength of our method.     

Clustered airline flight scheduling: Evidence from airline deregulation in Korea

This paper explores the impacts of competition level on airline scheduling in the Korean domestic short-haul routes where a hub-and-spoke system is not the optimal air transport network strategy. The empirical findings using the Korean airline panel data for the period 2006–2010 suggest that competition leads to less differentiated departure flight times as expected from spatial competition theory. Unlike the previous study on the U.S airline industry, the degree of this tendency for less differentiation differs across the type of routes: the Jeju island routes (leisure type) and the inland routes (business type), in the deregulated period. Following the May 2008 Deregulation Act we find an increasingly clustered pattern of airline scheduling in the Jeju island routes where there have been competitive pressures associated with new low cost entrants. This recent evidence would imply that airline carriers strategically schedule departure flight times and allocate flights between routes as competition increases in the deregulated period.     

Modelling of aircraft rotation in a multiple airport environment

The objective of this paper is to develop a simulation model to simulate aircraft rotation in a multiple airport environment. The developed aircraft rotation model (AR model) consists of two sub-models, namely the aircraft turnaround model, which describes the operation of aircraft turnaround activities at an airport and the Enroute model, which simulates the enroute flight time of an aircraft in the airspace between two airports. Delays due to operational disruptions from aircraft turnaround activities are modelled by stochastic variables in the aircraft turnaround model. Uncertainties from schedule punctuality are modelled by probability density functions in the Enroute model. The proposed aircraft rotation model is employed to carry out a case study by using real schedule and punctuality data from a European schedule airline. Simulation results when compared with observation data validate the effectiveness of the aircraft rotation model. The proposed model is also found suitable for airlines to serve as a schedule planning and analysis tool.     

Airline ground operations: Optimal schedule recovery with uncertain arrival times

Airline operations are subject to a number of stochastic influences which result into variable ground and block times for same flights on different days. Our research explores how airline operations control centers may benefit from an integrated decision support system for schedule recovery during aircraft ground operations. In this paper, we study the sensitivity of an optimal set of schedule recovery options towards uncertain arrival times. The calculation of recovery options is based upon an integrated and iterative scheduling and optimization algorithm, which incorporates uncertainties for arrival flights as a function of a given look-ahead time. Potential recovery options include stand re-allocation, quick-turnaround, quick passenger transfer, waiting for transfer passengers, cancellation of passenger or crew connections, and arrival prioritization. Within a case study setting at Frankfurt Airport, 20 aircraft turnarounds are analysed during a morning peak with their respective estimated arrival times (including potential arrival delays). The analysis of simulation results reveals an almost identical set of selected recovery options under high uncertainty circumstances and from post-operational point-of-view, which indicates high solution stability.     

A time–space network model for unit load device stock planning in international airline services

Unit load devices (pallets, containers, etc.) are used to move luggage and air cargo on wide-bodied aircraft. This paper examines a case study of the number of devices needed by an airline for international scheduled services. Unit load device movements between airports require planes to load and deliver. The stock of the unit load devices is thus influenced by the airline’s scheduled services. Based on a recurring weekly schedule, this study develops a time–space network to formulate mathematical programming models for minimizing device quantities. This model is applied to assess the preparation level of unit load devices for the various service networks for a Taiwanese airline.     

The cost of aircraft noise – Does it differ from road noise? A meta-analysis

This paper aims at studying the difference in cost between aircraft noise and road noise using meta-analysis. 90 NDI estimates have been gathered from the literature (a total of 53 studies), out of which 44 are estimates for aircraft noise and 46 are for road noise. The results of the meta-regression suggest that aircraft noise costs somewhere in the range of 0.40 and 0.60 percent more per increased dB than road noise. Knowing the associations between these costs of noise pollution can be a convenient tool for planners and policy makers, offering an opportunity to make predictions of aircraft noise when only estimates of road noise are available, and vice versa.     

Linking formal controls to motor carrier performance: Curvilinear and interaction effects

We examine the relationships between formal management controls (FMCs)—activity controls and output controls—and motor carriers’ operational and market performance. Using nonlinear structural equation modeling, we identify curvilinear and interaction effects of FMCs on carrier performance. We contribute to theory by providing evidence that the relationships between FMCs and performance are more complex than previously theorized. Namely, excessive activity control will adversely affect market performance, especially when output control is low. However, when output control is high, increasing activity control improves market performance—up to a point. Accordingly, we provide managerial guidance on appropriate levels of FMC use.     

Management of airport congestion through slot allocation

The lack of airport slots (the time allocated for an aircraft to land or take off), particularly at airports which experience congestion, have reached unmanageable proportions in recent years. The International Civil Aviation Organization (ICAO) records that, by the end of 1997, there were 132 slot controlled international airports. The World of Civil Aviation, 1997–2000. ICAO Circular 273-AT/113, p. 12 (118 year round and 14 during peak seasons). Between 1989 and 1998 the reported number of commercial aircraft in service increased by about 60% from 11,253 to 18,139 aircraft. In 1998, 1463 jet aircraft were ordered, compared with 1309 in 1997, and 929 were delivered compared with 674 aircraft in 1997. In 1998, the total scheduled traffic carried by airlines of the 185 Contracting States of ICAO amounted to a total of about 1462 million passengers and about 26 million tonnes of freight. These figures¹ are reflective of the rapidly increasing frequency of aircraft movements at airports, calling for drastic management of airport capacity. To cope with the demand, airlines are forming strategic alliances with themselves by utilizing such commercial tools as franchising, leasing and interchange of aircraft. The management of airport capacity through slot allocation is a critical consideration for the world aviation community. This article analyses the problem and discusses various issues related thereto.     

Aircraft operational costs and turnaround efficiency at airports

The aim of this paper is to investigate the relationship between flight schedule punctuality and aircraft turnaround efficiency at airports, in order to minimise system operational costs and meanwhile to maintain a required level of schedule punctuality. Investigations of aircraft operational costs, passenger delay costs and airline schedule time-opportunity costs are carried out in this paper. A mathematical model is applied to simulate aircraft turnaround operations by considering the stochastic effects of schedule punctuality as well as aircraft turnaround performance. Two numerical examples demonstrate the performance of the aircraft turnaround model. Results show the significance of a proper use of schedule buffer time in maintaining schedule punctuality performance.     

Fuel burn rates of commercial passenger aircraft: variations by seat configuration and stage distance

Aircraft fuel consumption is a very large component of airline costs. Fuel burn is also very important because it is highly correlated with emissions and contributes directly to transport externalities. This paper calibrates fuel burn in kilos per seat per nautical mile for aircraft using the EMEP/EEA aircraft inventory database. We then employ the model with OAG flight schedule data to evaluate fuel burn by flight routes and aircraft types at a global scale. The paper shows comparative fuel use among different distance based markets as well as among a variety of routes in the long-haul market. The results show geographical heterogeneity of fuel burn rates among a variety of routes, while controlling for seat configuration and stage distance. The paper finds that stage lengths centered on 1500–2000 NM have the lowest fuel burn rates under current technology, fleet composition, and seat configuration. These findings, together with comments on the viability of long range flights provide better understandings not only for the carbon taxation debates but also for operational efficiency of current aviation markets. The lower rates for moderate distance flights seems to favor networks without extreme links, and supports the use of a hub connection scheme.     

A robust mathematical model and heuristic algorithms for integrated aircraft routing and scheduling,with consideration of fleet assignment problem

One of the most important airline's products is to determine the aircraft routing and scheduling and fleet assignment. The key input data of this problem is the traffic forecasting and allocation that forecasts traffic on each flight leg. The complexity of this problem is to define the connecting flights when passengers should change the aircraft to reach the final destination. Moreover, as there exists various types of uncertainties during the flights, finding a solution which is able to absorb these uncertainties is invaluable. In this paper, a new robust mixed integer mathematical model for the integrated aircraft routing and scheduling, with consideration of fleet assignment problem is proposed. Then to find good solutions for large-scale problems in a rational amount of time, a heuristic algorithm based on the Simulated Annealing (SA) is introduced. In addition, some examples are randomly generated and the proposed heuristic algorithm is validated by comparing the results with the optimum solutions. The effects of robust vs non-robust solutions are examined, and finally, a hybrid algorithm is generated which results in more effective solution in comparison with SA, and Particle Swarm Optimization (PSO).     

Truck scheduling for ground to air connectivity

A critical link in the overnight package business is the on-time arrival of trucks at airport terminals. Truck delays can delay the package sorting and transfer process, which can in turn delay aircraft departures from the local terminal, as well as aircraft departures from hub terminals that depend on timely aircraft arrivals. This paper models the airport terminal as a queueing process with random bulk arrivals. Predictions are provided for expectation, and standard deviation, of arrived work. From these predictions performance measures are developed for sort end time and sort starvation. Particular attention is given to scheduling the start time for the sorting process, to balance a trade-off between maximizing sort productivity and minimizing the end time of the sort. The methods are being implemented as a web-based scheduling tool.     

Scheduling reefer mechanics at container terminals

This paper discusses the scheduling of reefer mechanics at container terminals. Reefer mechanics plug and unplug reefer containers such that due times are met. We outline the resulting scheduling problem and two simple heuristics. Subsequently, we present a simulation model to analyze the scheduling methods and the reefer-related processes in a realistic dynamic framework. Some results from the simulation experiments are also presented. They demonstrate the applicability of the heuristic and the use of the simulation model in practice. The simulation study was carried out for a real container terminal in the port of Hamburg, Germany.     

Relay network design in freight transportation systems

This paper provides techniques, heuristics, and algorithms for the location of a minimal number of relay points on a highway network that satisfies the driver-distance constraint––a driver leaving a distribution center does not travel for more than t miles before which he/she returns back to the originating point or rests before moving on further. Straight Route and Detour versions are considered. Empirical evaluations of the proposed heuristics on road networks are performed. The results indicate that the Straight Route version is computationally efficient but locates a larger number of relay points than the Detour versions.     

An integrated model for stock replenishment and shipment scheduling under common carrier dispatch costs

We examine a joint inventory replenishment and shipment scheduling problem that arises in the context of a vendor-managed inventory (VMI) arrangement. Since a temporal shipment consolidation policy is being implemented, the inventory requirements at the vendor are affected by the timing and quantity of shipment release. The vendor’s problem is to determine an integrated policy for inventory replenishment and shipment release and to set its parameters. We develop analytical models for computing such integrated policies where it is economical to use common carriage for outbound transportation. We propose algorithmic approaches to set the optimal policy parameter values.     

Willingness to pay for travel time reliability in passenger transport: A review and some new empirical evidence

This paper reviews and critiques the modelling frameworks and empirical measurement paradigms used to obtain willingness to pay (WTP) for improved travel time reliability, suggesting new directions for ongoing research. We also estimate models to derive values of reliability, scheduling costs and reliability ratios in the context of Australian toll roads and use the new evidence to highlight the important influence of the way that trip time variability is included in stated preference studies in deriving WTP estimates of reliability in absolute terms, and relative to the value of travel time savings.     

A multi-objective approach to scheduling joint participation with variable space and time preferences and opportunities

Activity scheduling supports activity-based analysis in travel demand management and promotes a potentially popular traveler assistance service. A multi-objective approach is proposed to schedule joint participation of multiple individuals, in which the candidate space-time opportunities for joint participation are identified by a concept of time-varying network-based prisms, and optimal opportunities for joint participation are determined by the non-dominated sorting genetic algorithm-II (NSGA-II) with four objectives (i) minimizing cost for congestion charges, (ii) maximizing participation desirability of time-of-day, (iii) minimizing total travel distance and (iv) time in the trips of multiple individuals. A scenario of joint participation among four people is designed and implemented to demonstrate the feasibility of this approach. The results suggest that this approach has the ability to schedule activities within real situations.     

Slot auction in an airport network with demand uncertainty

This paper investigates the effectiveness of airport slot auction by developing a two-stage model, which distributes slots among competing airlines using an ascending-bid multi-unit auction. Airlines assign different values to slots at peak and off-peak periods, and each carrier has its private (subjective) forecast of future demand. Conditional on the slots available to them, airlines compete in frequency, fare, and aircraft size over a congested airport network. The market outcome under such a scheme is benchmarked to those under an ex ante allocation and an ex post allocation by a social planner. Comparison results suggest that the auction-based scheme is inferior to the other two schemes when there is little fluctuation in demand, whereas the auction-based system is more effective when there is substantial demand uncertainty. Auctioning some grandfathered slots can improve social welfare but the marginal effect may diminish quickly.     

Drivers of airline loyalty: Evidence from the business travelers in China

This paper examines the key factors that determine business traveler loyalty toward full-service airlines in China. Based on literature review and panel interview, ten airline attributes under three categories were derived: (a) operational factors: safety, punctuality, and aircraft; (b) competitive factors: frequency of flights, schedule, frequent flyer program, ticket price, and reputation; and (c) attractive factors: in flight food & drinks and in flight staff service. We surveyed 2000 Chinese business travelers on domestic flights, obtaining 462 usable questionnaires. Hierarchical regression analysis reveals that reputation, in-flight service, frequent flyer program, and aircraft have the greatest influence in driving airline loyalty.