After the collapse and the rebound in passenger traffic in 2009 and 2010, came the consolidation. Passenger traffic across the leading airports grew a little more than 5% last year. Yet, if this marks a return to more normal overall traffic-growth rate levels, it does not quite feel like business as usual just yet.
The economic picture, particularly in Europe, remains fragile at best - fuel is a headwind no airline can escape and consolidation continues through mergers, joint ventures and airline failures.
All this is making airlines in many markets, although not all by any means, cautious and selective over capacity. Airports may well benefit in the long run from this discipline through stronger airlines, but these factors make competition for traffic fierce.
Airports body ACI Europe highlights a two-speed aviation market that is developing in the continent perhaps most under pressure - Europe. It points to sharply different growth rates between those airports within the European Union and those outside the grouping in countries such as Russia, Turkey and Iceland. Airports in the latter countries enjoyed double-digit passenger growth in the first quarter of this year. This compares with a paltry 1.7% growth across EU airports.
"This is damning evidence of the impact of the unresolved sovereign debt crisis and punitive national aviation taxes," says ACI Europe director general Olivier Jankovec.
But the picture is less clear-cut, with marked winners and losers. While key hubs in buoyant markets led by fast-growing carriers, such as in Istanbul and Moscow, continued to see double-digit growth, established hubs in the heart of the flat-lining European economy retain respectable growth. Traffic figures for 2011 show the three biggest European hubs - Frankfurt, London Heathrow and Paris Charles de Gaulle - were among the four fastest growing of the 10 biggest hubs.
"March passenger figures continue to reveal strong resilience for large hubs - with the exception of those in Greece, Spain and Italy, where many airports are losing traffic," says Jankovec of the European airport fortunes.
Passenger levels at Heathrow and Charles de Gaulle grew 7% and 6% respectively in the first quarter, and International Airlines Group chief executive Willie Walsh stressed the robust performance of London during a recent results call. "Although the UK economy is in recession, we are not seeing any evidence of that in our Heathrow hub," he says.
Few of the traditional major hubs have lost ground over the year. But over the last decade they have instead been joined by fast-growing airports from emerging regions.
Beijing, Guangzhou, Dubai and Jakarta airports, which ranked 41st, 77th, 80th and 91st in 2001 respectively, all now figure in the top 20 biggest airports in 2011 by passenger numbers. The likes of Shanghai, Istanbul, Kuala Lumpur - all outside the top 60 biggest airports 10 years ago - seem destined to join them in the future.
Most of the fast-growing airports in 2011 reflect expanding home carriers, but one interesting example was Barcelona El Prat airport. Passenger numbers were up 15% as one home low-cost carrier Vueling picked up its growth stride again after a period of consolidation following its merger with ClickAir and Irish carrier Ryanair arrived at the airport.
However, its traffic this year will be hit by the collapse in January of Spanair, compounding the impact of the country's economic woes. While growth at the airport in the first quarter is up 3%, this compares with a rise of almost a fifth at the same stage last year.
Those airports where traffic slipped in 2011 in some cases stem from either damaging events such as the fallout from the devestating earthquake and tsunami in Tokyo, which hit Japanese traffic, or the closure of airspace during the Arab Spring and political unrest which wiped a quarter off Cairo airport's passenger totals in 2011.
Economic factors were a major contributor in some traffic falls during 2011. Passenger levels at Spanish and Greek airports overall remain under pressure, down 6% and 12% respectively according to ACI Europe figures for March. In some other cases, actions of particular carriers - such as Ryanair grounding large elements of its winter capacity at London Stansted - took a toll.
Traffic falls at some of the North American airports in part reflect changing dynamics resulting from mergers, which has put some formerly competing hubs into the same airline camp. "What you find is because of this there is, in effect, a scarcity of resources. These resources are flowing out to the strongest hubs," says US aviation consultant Robert Mann. Several US airports have seen passenger levels slip as they move away from hub operations to point-to-point routes. "What some have now is very little transfer traffic and it's all about O&D traffic with smaller-gauge equipment," says Mann. He notes that up to two-thirds of hub airport traffic could be transit, while focus airports may be 100% O&D traffic. "But there is still room for growth both in the gauge of equipment and number of non-stops," he adds.
The continued capacity discipline of US carriers is also keeping airports hungry for passengers. "That is a function of the pricing power," Mann says, as airlines look to recover the price of fuel through higher fares. "The business traveller absorbs it, but the leisure and discretionary travel market is way down," he adds.
So what are the priorities for those airports that may be on the fringes that find themselves facing more intense competition. "They can make certain their operations are as efficient as possible and strive for the right airline and destination mix, to make it somewhere people want to fly." says David Feldman, managing partner at Exambela Consulting.
Speaking during a recent conference held in The Hague on airport hubs, organised by Dutch aviation research grouping Airneth, aviation consultant Jan Veldhuis outlined opportunities still exist for second-tier airports to create a niche as more efficient aircraft are added to airline fleets. He sees an opportunity in connecting either small markets from major hubs or medium-sized markets between themselves. He notes this is the strategy that Turkish Airlines and Emirates are following, aided by the geographical location of their hubs, which are within an eight-hour flight of most of the world's population. Second-tier cities in large markets, for example Guadalajara, Durban, Novosibirsk, Bengaluru might provide a wealth of opportunities for airlines that can integrate them into their networks.
While Dubai, Istanbul and other hubs in emerging countries are attracting most of the attention because of their impressive growth figures, some second-tier European airports are busy reinventing themselves as "next generation hubs". Airports such as Brussels or Dusseldorf - which has actually trademarked the name "Next Generation Hub" - cannot rely on a single, very-large airline to guarantee their hub status and therefore must get creative and develop other strategies.
Ulrich Topp, director of aviation marketing at Dusseldorf airport, says it is following a strategy to consolidate its position as Germany's third air hub. Here, a non-reliance on a single carrier is key: Air Berlin and Lufthansa are both equally important to the future of Dusseldorf.
The dangers of an airport having all its eggs in one airline basket is nothing new for airports. The impact is underlined by the recent collapse of Malev and ensuing loss of traffic for its Budapest hub. Despite rapid moves by other carriers, including traffic-magnet Ryanair, passenger numbers at the airport were nearly 5% down over the year. This compares with growth of 9% in 2011 and has already forced it to temporarily close one of its older terminals in a bid to cut costs.
A decade on from the demise of Belgian carrier Sabena, Brussels airport has yet to return to the same highs. While the consolidation of Sabena's successor Brussels Airlines and its focus on Africa has made it possible for Brussels to preserve the semblance of a hub, passenger levels of 18.6 million in 2011 were still three million down on 2001.
Léon Verhallen, head of aviation marketing at Brussels airport, presented the Belgian airport's plan to recover its position among Europe's top airports. The key to its plan is focus and location.
Verhallen explains the focus is not only on traditional destinations in Europe and Africa - Brussels Airlines offers the second-largest number of seats per week between Europe and Africa - but also on another emerging market: India. Jet Airways' choice of Brussels as a base for its "scissors-hub", a middle-point connecting three Indian gateways - Delhi, Mumbai and Chennai - with three North American airports - Toronto, New York JFK and Newark - has made Brussels one of Europe's main gateways to India, with a large percentage of passengers on these routes starting their journey outside Belgium.
Brussels' location is another important asset: at the centre of a densely populated catchment area spanning several neighbouring countries, and providing strong O&D traffic. Brussels' relative distance from the Star Alliance's hub cluster in Central Europe and its location, a Star Alliance wedge between SkyTeam-dominated Charles de Gaulle and Amsterdam and Oneworld's Heathrow, might represent a opportunity for both Brussels Airlines and the Belgian airport.
Europe's largest new airport in a generation in Berlin, while now further delayed, will enter the fray next year. The combined passenger numbers at the existing Tegel and Schoenefeld sites of 24 million in 2011, means Berlin's unified Brandenburg International airport would surpass Dusseldorf and Brussels by passenger number to rank inside the top 60 airports worldwide.
The new BBI airport was set to open early in June but - much to the chagrin of its largest operator Air Berlin, which plans to use the new facility to develop hub operations - its launch has been further postponed after technical problems with the fire-protection systems. Now, the airport's operator does not expect to open Brandenburg International until March 2013. The operator had already pushed back the original opening from October 2011 over security compliance issues.
"It doesn't change the big picture of the project," says Marjan Schöke, head of network development for the new airport. The new airport unifies the city's airport system, which has been split since the city was divided after the Second World War.
The iconic Tempelhof airport has already closed and both Tegel and Schonefeld will follow when the new airport opens. "Obviously there is a big growth coming from the local market, with Berlin being one of the most attractive destinations," says Schöke.
Passenger numbers to Berlin have doubled during the past 10 years and he expects growth to continue. "We have a very good O&D market. At the same time, with our target carriers we have developed hub waves.
"We had last year 24 million passengers [in total] and if you compare that to other hub airports, it is has very low - around 1 million - transit passengers," he says. "It was only 2010, when Air Berlin started to implement something similar to a hub wave." Air Berlin has planned to introduce six daily "waves" of flights, specifically tailored to Brandenburg.
"We have seen a big change [in short-haul traffic] with more high-frequency flights in Europe, so its easier for connecting traffic," adds Schöke. "We have seen a big increase in long-haul flights, much of it driven by Air Berlin, Asian and Gulf carriers. But we have some very big unserved markets, both in Asia and the USA. We still have much more demand than we have direct capacity."
As Brandenburg International's biggest customer Air Berlin is central to its development, especially with the airline's recent entry into Oneworld, which gives it alliance hub status. "It does effect our strategy," says Schöke.
"If we are able to use the Oneworld feeder traffic, that enables us to talk differently than where we were a couple of years ago. Other Oneworld carriers in Asia are candidates [for long-haul]."
But the economic situation in Europe has probably placed the most pressure on smaller, regional airports. "Passenger growth at regional airports is generally weakening, reflecting their exposure to the present economic environment," says Jankovec.
Feldman believes regional airports with the right attributes can still prosper and thrive. "Airports like Edinburgh and Hamburg and regional airports that serve vibrant communities and have been, and will continue to be, well connected to the big European hubs," he says, as well as increasingly to the Gulf hubs. " I don't think they are at risk at all."
But he acknowledges there are some geographies where "there are still too many airports". And some of these, especially with the tough climate limiting start-up ventures to fill gaps, are left with few choices ahead. "They are in a much more difficult situation, where it is Ryanair or nothing," he says. "They are airports that generally do not serve strong and viable market bases."
Additional report Miquel Ros