A irports around the world are congested. At the beginning of this year, the International Air Transport Association (IATA) published data showing global air passenger traffic has now surpassed pre pandemic levels, with domestic traffic increasing by 13.7% and international traffic growing by 0.9% in comparison to 2019 levels.
With more people travelling again and more flights needed to accommodate the increase, airports around the world are becoming busier. The industry is considering how best to manage the expected congestion by querying whether there is a better way to manage slot allocation, and asking if expansion is even a realistic goal.
Slots – The current system
One way of managing airport congestion is through more efficient slot coordination. Today, the Worldwide Airport Slot Guidelines (WASG) act as a global standard, which are jointly published by IATA, Airports Council International (ACI), and the Worldwide Airport Coordinators Group (WWACG).
These guidelines set out the rules surrounding the operation of the slot system that IATA urges all airports to follow. “Evolution, not revolution, is the way forward,” says Chris Goater, head of corporate communications at IATA.
Goater admits that the slot guidelines, implemented around the world, “can’t solve the airport capacity crisis”, adding that creating more capacity is the only real solution.
“It’s the job of the slot rules to ensure the capacity that is available is allocated fairly and transparently and as efficiently as possible, and we would argue that they achieve that,” he says.
Current slot guidelines mean that airlines have to use 80% of their take-off slots if they want to keep them.
“The 80:20 slot rule is an area of debate with some arguing that there should be a 90:10 rule,” says Goater. “Moving to a 90:10 for example might mean that airlines don’t want to lose their slot. So, they will use that slot anyway but the flight may not be particularly full. That’s not a particularly useful use of resources and not the best for the environment; historically we believe the 80% margin is right and is the sweet spot when it comes to slot coordination.”
Goater maintains that the current slot rules do not hold back competition nor are they holding back route expansion. He sees problems at the very congested airports caused simply because “they have not been allowed to expand”.
Airport expansion
Expansion seems to the logical solution to alleviating congestion at a crowded airport – adding an additional runway, a few more taxiways and extra gates would potentially solve the problem. Airport expansion is tremendously difficult, however, and often highly politicised that can lead to years of delays and numerous consultations, not to mention protests by local residents and
environmental groups.
In June of this year, new research by CE Delft commissioned by green group Transport & Environment, suggested that thousands of cases of dementia, high blood pressure and diabetes across the United Kingdom could be linked to particles that have been emitted by aircraft. The study outlines that around six million people in the UK, or 9% of the population that live within a 20km radius of London Gatwick, Heathrow, Stansted and Manchester airport are being exposed to ultrafine particles (UFP’s) from aviation.
“Airports should aim to be good neighbours, and not damage the health of those living around them,” says Tim Johnson, director at the Aviation Environment Federation. “The results of the study from T&E indicate that the health impacts from ultra-fine particles (UFPs) are both serious and can be reduced. Industry and Government should work together and consider all options to aim for compliance with WHO guidelines on air pollution.”
The report claims that people living within a 5km radius of an airport breathe in air that on average contains between 3,000 to 10,000 UFP’s per cm3 emitted by aircraft. To put that into context, people living in typically busy, built-up city centres are exposed to around 3,000 to 12,000 particles per cm3. This means that planes are exposing residents around airports to similar levels of ultrafine particles that are seen in busy urban centres. More broadly across Europe, these ultrafine particles may be associated with 280,000 cases of high blood pressure, 330,000 cases of diabetes and 13,000 cases of dementia, according to this new research. The study extrapolated reported cases of these illnesses discussed around Amsterdam’s Schiphol airport and has given the first ever estimate of health effects linked to aviation related UFP’s in Europe.
With such alarming data points, environmental groups are lobbying hard for a curb on any airport expansion and are even pushing for existing flights to be limited.
“If the Government is serious about protecting the UK population from the significant health risks connected with ultra-fine particles, a flight cap to meet air pollution goals is the only way to guarantee outcomes, with regular reviews to measure performance and ensure compliance,” says Johnson. “This cap is not without precedent, as it is already common practice to achieve aircraft noise targets and commitments.”
The alarmist report states that any airport expansion would result in more particles emitted by the increase in aircraft.
With airport expansion such a political hot potato, Professor Richard Steinberg from the London School of Economics claims that better slot management is a more acceptable alternative to airport expansion. “We don’t need to expand airports; we need a better way of managing slots,” he says.
The world airline slot guidelines put in place by IATA are described as a ‘process to maximize the efficient use of airport infrastructure’. However, it is believed that in order to combat the congestion problem at some airports auctioning slots would be a better way of maximising infrastructure.
Professor Steinberg believes that auctioning slots is the way forward for airport coordination, and that this urgently needs to be rectified to combat the congestion issues witnessed in airports around the world.
“Under current regulations, if a runway slot is used by an airline 80% of the time over a season, then it has the use of that slot for the following season,” said Steinberg. “This has resulted in the wasteful but common practice of airlines organising flights with empty planes, called ‘ghost flights’, which allow airlines to retain their slots in perpetuity. Slot auctions would eliminate incentives for airlines to schedule ghost flights, leaving more slots for bona fide flights.”
Steinberg argues that even without the issue of ghost flights, economic theory and historical data “strongly indicate” that a market-based approach of slot auctions would make far more efficient use of available slots, resulting in increased airport capacity.
“This idea of auctioning slots has been around since the 1980s,” says Steinberg. “Vernon Smith the Nobel Prize winner in economics in 2002 said 40 years ago that maybe we could allocate runway take-off and landing slots by auction, and it would be a way of raising money for airports, and also would act as a way of controlling congestion.”
Steinburg believes that the implementation of slot auctions at airports around the world would also reduce carbon emissions produced by airlines.
“By saying let’s just build bigger and bigger airports to combat congestion is like saying the country’s motorways are congested, so let’s increase the number of motorways and the country will be better off,” he says. “If slots are auctioned, it allows for an increase in competition, generally meaning that resources are allocated more efficiently. The system today is essentially non-competitive. Increased competition would reduce costs and reduce the number of unnecessary flights airlines will operate – these ghost flights – in order to keep the slot.”
Under current guidelines, take-off and landing slots are allocated twice a year, something which Steinberg agrees with and could keep the same.
“Slots are allocated every six months, so I would recommend keeping this allocation. There’s a reason why that’s worked. Every six months means that it considers changes in airports and demands,” he says.
Sao Paulo’s Congonhas Airport, which has been dubbed “the most congested airport in Brazil, and the world,” has a slightly different way of managing airline slots, which seems to be working. Slot management at Congonhas differs from other airports within Brazil and around the world due to its unique domestic demand, and infrastructure limitations due to the airport’s location within Brazil’s largest city.
The airport faces unique challenges, such as its high demand, limited operational hours, and infrastructure constraints. The Herfindahl-Hirschman Index (HHI) – which measures the concentration of the market – at Congonhas was around 4,000 before the new slot regulations were brought in, much higher than the national average of 3,000, indicating a lack of competition and a concentrated market. In addition, airlines with large market shares were using slots inefficiently, contributing to high airfares and reduced competition. Additionally, slot hoarding – where dominant airlines retain slots without fully utilising them – made the problem worse at the airport.
Speaking with Rodrigo Neves Martins, technical manager of air services registration and slot coordination at Congonhas, he explained how the airport co-ordinates its slots differently, in order to manage the strong domestic demand that the airport experiences.
“The development of Congonhas’ slot management system followed a structured, consultative process involving multiple stakeholders,” he explains. “Studies were conducted to define the main issues related to slot allocation at Congonhas. Existing literature on slot allocation and competition was also reviewed. The problem was validated by representatives from the aviation industry, ensuring that the regulatory approach addressed real market concerns.”
“A call for contributions was made to gather input from industry stakeholders and experts. Over 122 individual contributions, six full studies, and 20 annexes were considered during the 34-month process of developing the new regulation.”
When asked if Congonhas would be better or worse off from following the WSG guidance with no exceptions, Neves Martins said, “the airport would be far more congested if the airport did not implement its own slot management rules”.
Congon has created the ‘local rule’ that works specifically for the airport. The new rules reserve 100% of newly available slots for new entrant airlines, allowing up to 18 slots per day for these carriers. This move is designed to encourage competition and break the dominance of established airlines already operating out of the airport. To prevent any one airline from monopolising operations, a 45% daily market share cap has been imposed, ensuring a more level playing field.
Additionally, a fast-track system has been introduced for smaller airlines with a domestic market share of 1-2%, which would allow them to quickly secure valuable slots and compete more effectively. Airlines must also meet strict operational requirements, including having at least five aircraft in service and meeting specific passenger traffic benchmarks, ensuring that only capable airlines receive slots.
As global air travel continues to exceed pre-pandemic levels, solving airport congestion has become a critical issue. While airport expansion may seem like an obvious solution, political and environmental challenges are hindering any meaningful expansion in the more congestion jurisdictions. Experts, such as Professor Richard Steinberg, continue to advocate for improved slot management, including the introduction of slot auctions to ensure more efficient use of airport infrastructure. The example of São Paulo’s Congonhas Airport demonstrates the potential benefits of localised slot management. By implementing tailored rules that reserve slots for new entrants, limit market share dominance, and fast-track smaller airlines, Congonhas has successfully tackled congestion and improved competition through altering their slot management rules. These innovative approaches suggest that better slot management, rather than expansion alone, can be a viable and immediate solution to the growing problem of airport congestion worldwide.