Understanding the building blocks of aviation capacity

Catya Zuniga and Geert Boosten, from the Amsterdam University of Applied Science, discuss how best to define aviation capacity.

Aviation capacity has to consider departing and arriving aircraft

Both Airbus and Boeing’s market outlooks forecast a continuous annual air traffic growth of 2.9 per cent, towards 4.8 per cent until 2036. In 2019, European carriers grew by 4.8 per cent (revenue seat kilometre, RSK), whilst their capacity grew by five per cent (available seat kilometre, ASK). Although the current COVID-19 crisis is having a tremendous impact on aviation, we assume that, after recovery, aviation will once again find its growth path from the last decade.

Airport congestion

Continuous growth creates a paradox in which more aviation brings more economic growth, as well as increased delay and congestion. Therefore, one of the air transport industry’s major challenges is to find the sources of congestion and determine how to mitigate its attached effects, such as delays and their propagation through the global network of airports. Congestion appears when the demand exceeds the available operational capacity of the resources, such as the airport infrastructure, handling services or air traffic management, to mention a few.

Aviation capacity includes the runway

The congestion causes delays which have a major economic and environmental impact on the entire air transport system. Research (Ball et al, 2010) indicates that actual demand at the majority of U.S. airports can exceed the operational capacity, resulting in delays with significant associated costs; the nationwide impact of flight delays in the United States was estimated at over $30 billion in 2007 – out of which $8.3 billion was the direct cost of airlines – and this is still the case, as the FAA reports over $28 billion of delay-related costs in 2018. But, when access to airports is restricted, as in most of the busiest European airports, this will result in lost demand. According to IATA, in the European Union, the air traffic management (ATM) inefficiencies led to 10.8 million minutes of flight delays in 2012, costing €4.5 billion to airspace users and €6.7 billion to passengers, whilst producing 7.8 million tonnes of wasted CO2.

The challenging dilemma on how to act when congestion appears is either to enhance capacity or to manage traffic demand. Often, aviation seeks to enhance the capacity side of the equation. But we first need to understand what capacity is, by identifying the main drivers or factors that, in the end, will affect how many flights and/or passengers and cargo can be processed at an airport at any given moment.

Defining aviation capacity

A specific definition of airport capacity is missing; the most common defines the declared capacity as the number of hourly air traffic movements on a runway, or the runway capacity taking into account limitations by environmental criteria, such as noise and emissions. The complex nature of capacity, the lack of understanding, its drivers and characteristics, make it difficult to deal with capacity. Capacity seems to be a dynamic, interactive concept that is influenced by many factors or drivers. Therefore, before focusing on presenting a capacity definition, we will start by identifying the main technological and societal drivers that will determine the capacity of an airport system in a network-based approach. Next to these drivers, we want to point out the influence of the stakeholder’s business model on the factual airport capacity usage as one of the three main drives for capacity.

Technological drivers for aviation capacity

Queues result if measures are misjudgedThe most known and studied capacity driver is the technological driver for capacity, which englobes the aspects of capacity related to infrastructure, procedures, regulation and equipment (airside, in the airspace, on the apron and in the terminal), ground access and the size of the airport land. The declared capacity often relates to this capacity driver. In this context, the effect of the limited capacity of the airport system can be seen on the ground as passenger queues, in areas such as check in, security, waiting areas or limited aircraft stands; but, also, in the air, as aircraft entering on holding patterns or in ground delay. Airports have been implementing various efforts to deal with this situation, such as enhancing airspace capacity or expanding infrastructure. Although these approaches have (slowly) provided additional technical capacity, the demand is growing much faster than the new technical capacity can be realised. In addition, the options to increase the technical capacity are limited. These are capital intensive and do have a long-term horizon of realisation and implementation. Sometimes, it is even not possible to implement new capacity, due to geographical location or complex airspace operations. However, it is worthy to note that the technical capacity is the basis of an airport’s capacity. It defines what aircraft types can operate at the airport and what, in an unconstrained scenario, the maximum peak hour operations will be.

Societal drivers for aviation capacity

Congestion can result from incorrect measuresHowever, it isn’t often possible to operate the airport in an unconstrained capacity scenario. Environmental factors – such as noise-contour or controlled CO2 emission limitations imposed by local governments to protect surrounding neighbourhoods – will limit the airport’s capacity. Even though aircraft manufacturers have been very successful in improving the efficiency of, and decreasing the CO2 emission and noise production, each new generation aircraft, these efforts have not been enough to mitigate the impact of the fast demand growth. Therefore, our proposed second driver for capacity is called societal, which deals with the restrictions of society due to environmental, financial and political regulations to protect the quality of life in the region and/or to minimise the impact of aviation on climate change. These regulations and societal restrictions define to what extent society at large allows the airport and airlines to use the available technical capacity. In the context of societal capacity, special attention should be paid to the impact of aircraft OEM productivity. The production of new aircraft on a monthly (almost daily) basis adds impressive amounts of new aircraft to the worldwide fleet. These aircraft not only need adequate infrastructure on the ground and in the air, but also massive amounts of highly-skilled professionals to operate, handle and maintain these aircraft. It requires the training of new pilots, ATC controllers, MRO engineers and other aviation professionals in the short term. The big gap is that the training of highly-skilled professionals takes years, whereas aircraft can be constructed in weeks. So, the major challenge is to train these new aviation professionals in time, with the additional challenges of the upcoming retirement of very experienced and knowledgeable professionals, new technologies emerging and being implemented, and globalisation impacting procedures and regulations. This special societal factor of need for education stresses the need for a systemic approach when dealing with capacity. Aviation as a system is a global network-based industry, where capacity limitations at each airport as a node in the network will influence other airport nodes in the network and is influenced by external forces, such as globalisation, deregulation and market developments. Aircraft production is part of this system.

The impact of airport and airline business models

An airport isn’t just serving a specific local market; the so-called global-local paradox confronts the global operating aviation business with local concerns and arguments to balance economic and aviation growth with quality of life. The same mechanism ensuring that strong demand growth and success of aviation will result in congestion, and can be found in this paradox where more growth develops a stronger resistance in a region. Therefore, airport and airline business models play an essential role in the use of available technological capacity and societal factors. The success models of large full-service carriers are based on hub and spoke operations, which generate high peaks at airports. The appearance of a new type of business model – such as Low-Cost Carriers (LCC) – creates a new type of passenger with new needs. This model influences the capacity usage of many airports in a different manner. The LCC model is based on three main pillars of reduction: The flight operation cost (FOS), ground costs and system operation costs. The FOS are reduced by applying a point-to-point network model employing the same type of aircraft, which lead to the ‘same’ type of maintenance, crew training or fuel. The characteristics of the LCC business model have an impact on the aircraft turnaround time, but also on the airport usage. It will develop its own business model by anticipating a new type of airport user. A good example is the increased demand for slots at Amsterdam Airport Schiphol (AMS). When the societal constraint for 500,000 slots was almost reached, all airlines tried to acquire the last available slots and maintain operating flights just to ensure that the slots won’t be used. The business model of the airlines and airports encounters and triggers our third main driver for capacity, which stands for how airlines and airport de facto will use the available technical and societal capacity.

To conclude, aviation capacity might often be misunderstood as a general definition expressed in a number of aircraft movements per hour, day or year. In addition, this definition should consider other important drivers, such as the social factors and the business model of airlines and airports among other stakeholders. How to calculate capacity is a complex problem, consisting of reinforcing loops (resulting mainly in exponential growth) and balancing loops to control the impact of the growth on operations. More efforts, then, are needed to understand the drivers of capacity in this complex system to better plan and execute operations.


Geert Boosten discusses aviation capacityGeert Boosten is a Professor of Aviation Management at the Aviation Academy of the Amsterdam University of Applied Science and has over 31 years of experience in the airport business. He started working at Schiphol Airport in 1988 (where he stayed until 1999).

Boosten has gained expertise in many aspects of airport management, business development and strategy. As a Director of Corporate Strategy, he was responsible for Schiphol’s strategy, master planning and international development, as well as airport privatisation, regulation of fees and charges and new business development.

After leaving Schiphol, he advised airports and governments abroad on master planning, strategy and PPP-projects. Currently, Boosten is heading the airport aviation management research unit of the Aviation Academy. The focus of the applied research is on understanding the dynamics of airport capacity and the use of simulation tools in optimising the capacity usage.


Catya Zuniga discusses aviation capacityDr. Catya Zuniga holds a PhD in Telecommunication and System Engineering by the Autonomous University of Barcelona and completed postdoctoral studies under the supervision of Professor Daniel Delahaye at the French Civil Aviation (ENAC) School.

She has worked for the last few years as a professor for Spanish, French and Mexican universities; currently as an Associate Professor at Amsterdam University of Applied Science.

Zuniga’s main research has been focused on strategic and pre-tactical air traffic management and airport management. She has participated in European, Spanish and Mexican projects, such as STREAM (Strategic Trajectory Deconfliction to Enable a Seamless Aircraft Conflict Management); ATLANTIDA (New technologies applied to UAV’s for research and ATM development); a CICYT Spanish program (Discrete Event  Simulation Platform to improve the flexible coordination of land/air side operations in the Terminal Maneuvering Area (TMA) at a commercial airport); and, more recently, in a three-year project: Logistic Analysis of Air Traffic Operations in Mexico.

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