Airline network structure under demand uncertainty

In this paper, we provide another reason that may explain the adoption of the hub-and-spoke network structure in the airline industry. We show that when an airline has to decide on its capacity before the demand conditions are perfectly known, a hub-and-spoke (h&s) network structure by pooling passengers from several markets into the same plane helps the firm to lower its cost of excess capacity in the case of low demand and to improve its capacity allocation in the case of high demand.     

Characterisation of airline networks: A North American and European comparison

This paper contrasts the North American and European air transport markets using the extensive Official Airline Guide Databases. The pattern of network development in the two continental regions is examined using data for 1996–2008. The top ten carriers in both regions are analysed closely in terms of network structures and the basic geographical characteristics of these networks are highlighted. In addition, different measures of air transport activity such as seating capacity, and number of movements and of routes are compared. Visualisations of carrier networks are used to highlight the different network strategies operated by low cost and full service carriers. European carrier networks display many significant differences to North American carrier networks. European carriers generally organise their networks around one or two key nodes within the member state in which they are registered and generally do not operate interactive, continental-wide, multiple hub-and-spoke networks as do North American carriers. European and North American low-cost carriers operate much more interconnected networks than full services carriers. Southwest Airlines stands out as operating a particularly highly interconnected network.     

High-technology employment and hub airports

Deregulation of the US domestic air transport market in 1978 brought significant benefits to air travelers. The scheduled airlines have been given the freedom to improve their efficiency through being able to adopt efficient network strategies and more effective operating practices. This study examines empirically the advantages enjoyed by those passengers having access to a major hub airport. These often include more direct services, more frequent services and a wider range of interconnecting destinations. We seek to examine the benefits that local urban areas enjoy as the result of a major airline selecting the region as the fulcrum point for its hub-and-spoke services.     

Simulation analysis of factors affecting air route connection in China

In order to explore the impacts of various factors on air route connection, a probability model is constructed to simulate the Chinese airline network (CAN) in 2010, and the influences of tertiary industry output, degree and the spatial distance between two navigable cities on the analog results are discussed. Our research shows that, the opening of an air route is not completely determined by the potential air passenger flow of it, although the latter is playing a leading role. In addition, the connection probability of an air route is significantly affected by the tertiary industry outputs and degrees of corresponding two navigable cities, but little influenced by the spatial distance between them. Moreover, scale economies effect obtained from the increasing of degree is apparently greater than that brought by the developing of social economy, so CAN is more inclined to evolve into a hub-and-spoke network.     

Network development of low-cost carriers in China's domestic market

This paper examines China's LCC market and assesses the network development patterns from a geographical perspective. Overall, a nationwide LCC network has been formed with each individual LCC focusing on their own markets with limited overlap to avoid cut-throat competition. Spring Airlines has developed an advanced network supported by its core bases including Shanghai in East China, Shijiazhuang in North China, Shenyang in Northeast China and Shenzhen in South China. China United has developed a network radiating from Beijing. West Air and Lucky Air seem to be developing a hub-and-spoke network that contributes to the tourism industry in West China. The LCC network is affected by seasonal variations, especially for the routes to tourism destinations such as Haikou, Sanya and Xiamen. Hub cities, however, experience less seasonal impact. This research also finds that routes between 600 and 1800 km account for a large proportion of the LCC markets. Aviation policy, local government's subsidization and the expansion of the high-speed rail network have helped shape the landscape of China's LCC sector.     

Debunking some common myths about airport hubs

Much of the passenger air transportation market is served through hub-and-spoke operations with traffic being funneled through a number of major airports. This system has come under attack as protective of the airlines that center their operations on large hubs and is often as result, seen as not serving the public interest. This paper looks at some of the arguments that have been laid against the hub-and-spoke system. It does not offer a balanced perspective in that there are many problems with the system that are not touched upon here, but rather it seeks to question some of the economic logic that has been used to attack the hub-and-spoke structure. While the issues extend to many air transportation markets, the focus here is primarily on the US domestic situation.PrologueThe impacts of the events of September 11, combined with the move into economic recession in the US that was already underway at that time, have led to serious financial difficulties for many of the World's airlines. Some, such as Midway in the US, immediately sought bankruptcy protection whilst others, such as Sabena and Swissair in Europe, took a little longer to fade away. Most of those that remain, despite combinations of financial assistance, have been struggling in the current economic climate.The subject addressed here is not directly concerned with this issue, although there are important overlapping longer-term linkages. Rather it looks at the structure of the airline networks that dominate the provision of air services. These structures still remain, although there are inevitable changes occurring. This paper was initially drafted prior to the recent changes that have taken place in air transportation markets. It retains much of the original material that was presented at the Amsterdam meeting, with some minor up-dating. The theme may seem less important now than at the time of the meeting, but this, I would argue, is perhaps a premature view. The combination of derived demand, relatively easy market entry, lumpiness in investments, etc., have resulted over time in dramatic changes in the fortunes of the sector and individual actors in it. There are, though, a number of recurring themes that pose interesting questions for the applied economist and one of these is the nature of efficient networks.     

Integrators' global networks: A topology analysis with insights into the effect of the COVID-19 pandemic

In this paper we propose, to the best of our knowledge, the first analysis of the global networks of integrators FedEx, UPS, and DHL using network science. While noticing that all three networks rely on a “hub-and-spoke” structure, the network configuration of DHL leans towards a multi-“hub-and-spoke” structure that reflects the different business strategy of the integrator. We also analyzed the robustness of the networks, identified the most critical airports per integrator, and assessed that the network of DHL is the most robust according to our definition of robustness. Finally, given the unprecedented historical time that the airline industry is facing at the moment of writing, we provided some insights into how the COVID-19 pandemic affected the global capacity of integrators and other cargo airlines. Our results suggest that full-cargo airlines and, much more dramatically, combination airlines were impacted by the pandemic. On the other hand, apart from fluctuations in offered capacity due to travel bans that were quickly recovered thanks to the resilience of their networks, integrators seem to have escaped the early months of the pandemic unscathed.     

A note on the competitive advantage of large hub-and-spoke networks

This note explores the extent to which airlines operating large hub-and-spoke networks secure a competitive advantage. More specifically, this paper explores the intricate relationship which arises among productive efficiencies and profitability when the size of the hub-and-spoke network expands. To this end, Brueckner and Spiller (1991, International Journal of Industrial Organization 9, 323–342) airline economics model is generalized by allowing the size of the hub-and-spoke network to vary. The central result shows that, although the model exhibits decreasing returns to firm/network size (RTNS), nonetheless there is a competitive advantage to increasing the size of a network.     

Inter-urban competition and air transport in the deregulated era: The Nashville case

American cities are acting in a competitive environment as a result of forces like economic restructuring, capital mobility, and state devolution. Since the late 1970s, the federal government has dismantled the spatial boundaries of investment through the deregulation of several important sectors of the economy, including the airline industry. Transportation geographers have investigated how deregulation allowed airlines to develop a hub-and-spoke system. However, post-deregulation airline development has yet to be approached from the perspective of urban entrepreneurialism. Another layer of inter-urban competition has been added through new geographical patterns of airline investment, and capturing hub status through airport development may be especially valuable for mid-size cities. Most large cities have hub status, while small cities have no realistic chance of becoming major players in the air transportation network, thus making the hub an opportunity for mid-size cities. A case study of Nashville, Tennessee illuminates the strong local emphasis on airport expansion in the deregulated environment. Local business and government have been active and innovative, although not always successful, in policies that improve Nashville’s accessibility and position in the urban hierarchy.     

Hub-and-spoke network design for container shipping along the Yangtze River

Increasingly large, high-tonnage containerships are becoming a common sight on the Yangtze River, and the shipping network is being transformed accordingly. This paper reports the design of a hub-and-spoke network for a shipping company that is consistent with the characteristics of the Yangtze River. We first explore the economies of scale for container shipping by applying empirical data. Next, we propose a mixed-integer linear programming model, factoring in ship-operating and container-handling costs. We then conduct a numerical experiment and test the effectiveness of the model, and finally discuss the implications of hub-and-spoke shipping network design. The findings reported herein support the trends toward cargo concentration and port regionalization along the Yangtze River.     

Liner shipping hub network design in a competitive environment

A mixed integer programming formulation is proposed for hub-and-spoke network design in a competitive environment. It addresses the competition between a newcomer liner service provider and an existing dominating operator, both operating on hub-and-spoke networks. The newcomer company maximizes its market share—which depends on the service time and transportation cost—by locating a predefined number of hubs at candidate ports and designing its network. While general-purpose solvers do not solve instances of even small size, an accelerated Lagrangian method combined with a primal heuristic obtains promising bounds. Our computational experiments on real instances of practical size indicate superiority of our approach.     

Ports in multi-level maritime networks: evidence from the Atlantic (1996–2006)

While maritime transport ensures about 90% of world trade volumes, it has not yet attracted as much attention as other transport systems from a graph perspective. As a result, the relative situation and the evolution of seaports within maritime networks are not well understood. This paper wishes verifying to what extent the hub-and-spoke strategies of ports and ocean carriers have modified the structure of a maritime network, based on the Atlantic case. We apply graph measures and clustering methods on liner movements in 1996 and 2006. The methodology also underlines which ports are increasing their position by carriers’ circulation patterns on various scales. This research demonstrates that the polarization of the Atlantic network by few dominant ports occurs in parallel with the increased spatial integration of this area by shipping lines.     

Multi-port vs. Hub-and-Spoke port calls by containerships

This paper addresses the design of container liner shipping networks taking into consideration container management issues including empty container repositioning. We examine two typical service networks with different ship sizes: multi-port calling by conventional ship size and hub-and-spoke by mega-ship. The entire solution process is performed in two phases: the service network design and container distribution. A wide variety of numerical experiments are conducted for the Asia–Europe and Asia–North America trade lanes. In most scenarios the multi-port calling is superior in terms of total cost, while the hub-and-spoke is more advantageous in the European trade for a costly shipping company.     

Evolution trends of the network structure of Spring Airlines in China: A temporal and spatial analysis

Both the sustainable development of China's economy and the deregulation of the China air transport market have acted as a spur for the halting development of low-cost carriers (LCCs) in China. To analyze the development trends of LCCs' network in China, this paper took Spring Airlines, the only LCC in China as an example. First, the winter flight plans of Spring Airlines from 2005 to 2013 were collected. Secondly, the development trends of air transport network of Spring Airlines were explored with methods of mathematical statistics and social network analysis. Additionally, the development trends were analyzed from the levels of navigable cities, air routes and air transport networks. The results show that although Spring Airlines actively launched air routes between tourist cities with non-class I airports, its network has been transformed from a star structure into a complex one with multi-hubs. The development process of the Spring Airlines network can be separated into three stages. In addition, the problems and evolution trends of its network are discussed further.     

Optimal rail-road container terminal locations on the European network

The European transport policy has focused on sustainable transport solutions, among which intermodal transport is a key player. However, its efficiency is strongly dependent on the location of the container terminals. In this paper, a set of estimated potential locations is used as input for an iterative procedure based on the p-hub median problem that takes the variation in trans-shipment costs according to the number of trans-shipped containers into account. The final results are the optimal locations for European transfer terminals embedded in a hub-and-spoke network.     

Fair profit contract for a carrier collaboration framework in a green hub network under soft time-windows: Dual lexicographic max–min approach

This paper models a novel and practical bi-objective hub-location problem under a centralized carrier collaboration framework between one holding company and multiple carriers. The holding company first establishes a hub-and-spoke network in order to locate p hubs and to assign the center nodes to the located hubs. Then, it allocates the transportation routes of the hub network to the carriers. In contrast, the carriers should select an appropriate vehicle type to serve the transportation requests in a green hub network. The carriers are also able to meet the transportation requests within a certain time-window based on a soft time-window mechanism. Moreover, aiming to emphasize green transportation, a vehicle emission model is used to take into account CO₂ emissions of the vehicles where the fuel consumption is a function of speed level. Aiming to identify a win–win deal between the holding company and the carriers, a dual lexicographic max–min (LMM) approach is used in order to optimize their profits in a fair way. Finally, some numerical experiments are presented to demonstrate the applicability of the proposed methodology. The computational results show that not only the holding company and the carriers can better generate a fair profit contract among themselves using the LMM approach, but also both can obtain more profit in the worst case for their businesses rather than using the max–min approach. In addition, sensitivity analyses show that increasing the size of the soft time-window leads to a reduction in the delivery schedule violations, while results in raising the total profit. Moreover, the tax cost of fuel consumption as well as the number of potential vehicles has a substantial impact on both the fuel consumption and carrier’s profit.     

Estimating the impact of COVID-19 on air travel in the medium and long term using neural network and Monte Carlo simulation

The COVID-19 pandemic has had a substantial impact on the airline industry. Air travel in the United States declined in 2020 with significantly lower domestic and international flights. The dynamic change and uncertainty in the trend of COVID-19 have made it difficult to predict future air travel. This paper aims at developing and testing neural network models that predict domestic and international air travel in the medium and long term based on residents' daily trips by distance, economic condition, COVID-19 severity, and travel restrictions. Data in the United States from various sources were used to train and validate the neural network models, and Monte Carlo simulations were constructed to predict air travel under uncertainty of the pandemic and economic growth. The results show that weekly economic index (WEI) is the most important predictor for air travel. Additionally, daily trips by distance play a more important role in the prediction of domestic air travel than the international one, while travel restrictions seem to have an impact on both. Sensitivity analysis results for four different scenarios indicate that air travel in the future is more sensitive to the change in WEI than the changes in COVID-19 variables. Additionally, even in the best-case scenario, when the pandemic is over and the economy is back to normal, it still takes several years for air travel to return to normal, as before the pandemic. The findings have significant contributions to the literature in COVID-19's impact on air transportation and air travel prediction.     

Measuring the substitution effects between High Speed Rail and air transport in Spain

The main objective of this paper is to estimate the impact that the expansion of the HSR network has had on air transport in Spain by estimating the substitution effect between the two types of transportation. This paper considers the way that the HSR network has grown and how this growth could have affected air transport dynamically. The findings show that a dynamic vision of this substitution rate should be adopted, as opposed to assuming that the rate is constant, as has been the case in previous references. Although the rate varies significantly over the study period, only 13.9% of HSR passenger demand was found to have come from air travel during the 1999–2012 period, meaning that HSR and airlines would seem to offer more independent services than at first it might appear. This confirms the hypothesis as to the HSR’s great ability to generate its own demand. The substitution rate between the two transport modes seems to be closely linked to the way that any new stations are incorporated into the HSR network. Convergence between the seasonality of HSR and air transport has also been examined. The results show that it is difficult to talk of a real HSR transport network in Spain.     

Analysis of prospective airline mergers using a simulated annealing model

This paper examines the efficacy of a simulated annealing model of the US airline network in analyzing potential mergers between major airlines. The simulation performs satisfactorily in modeling the current hub-and-spoke system focusing on the effects on passenger routings, producer profits, and consumer welfare. In general, the simulated annealing model reasonably demonstrates the price and demand effects due to a merger of major carriers. While it cannot take into account all relevant information, such as labor union relationships and negotiating tactics, it can offers insight into the implications of airline mergers.     

Air traffic forecast and its impact on runway capacity. A System Dynamics approach

The uninterrupted growth of air traffic in Colombia has been reinforced since the 1990s by a public policy of liberalization of airspace, and by redirecting public and private investment towards the modernization and updating of airport infrastructures, giving in concession the busiest airports in the country, 19 to date. In the commercial air sector, and in this same period, the flag airline was privatized and new air operators, including low cost airlines (LCC), entered the market. Since 2012, air fares are completely deregulated. Consequently, in the last two and a half decades, passenger transport in Colombia grew by 863%. This important growth rate has been driven and led by the country's main airport, the Bogotá-El Dorado International Airport (BOG), in the capital of Colombia. But some technical reports consider the airport will reach its maximum capacity in the short term mainly because of its inability to expand its airfield (runway system). Due to this circumstance, the aeronautical public authority of Colombia gave course to the planning, design and construction of a new airport (complementary) on the outskirts of the city of Bogotá, which will enter the design phase in 2026/2027. Therefore, it is considered suitable the development of a traffic forecast for BOG in the medium term and to evaluate the impact of future demand on the runway capacity of the airport. Then, and due to the complexity of the air transport forecast, the use of System Dynamics (SD), is considered to be appropriate as an analysis approach. System Dynamics is based on feedback control theory and it is equipped with mathematical computer simulation models, which uses linear and non-linear differential equations. The results suggests a need to expand the airport case study (runway system) after mid-2019, where the current capacity utilization factor is around 100% and two to three runways will be required for the normal operation; after October 2022 the number runways required is set to three until the last period simulated (2023).