Reinvention of airports Norman Foster began in London and Hong Kong steps up

For the most part, airline passengers may be a captive audience. Yet even aside from the enforced internment of delayed or cancelled flights, travellers are spending longer in airports these days. And we expect more from them.

Hildegard Assies, Amsterdam-based co-founder of airporttrends.com explains: "The next-generation traveller is looking for new experiences at airports. Today's airports are therefore no longer just a space of passenger flows, but are evolving into unique locations that offer a sense of place for consumers on the move.

"Open and inviting terminals, especially designed with a local touch, are a great way to create and promote a sense of place and to create a unique traveller experience by encouraging exploration and discovery, and at the same time drive commercial revenues."

Cue high-profile architects to design them.

The new breed of iconic airport architecture was spearheaded by Norman Foster with London's Stansted Airport, opened in 1991, and he famously put his mark on Hong Kong's aviation gateway, Chek Lap Kok, in 1998 - a project he still regards one of his most important.

"I still find the scale of the project and boldness of the [Hong Kong] government's vision remarkable - it was one of the most ambitious construction projects of modern times," Foster says.

It's hard to imagine that the site of Hong Kong International Airport (HKIA) was once a mountainous island, reduced from its 121-metre peak to a six-metre-high plateau, he says. And the airport's glazed perimeter is nearly 5km long.

"While in building terms, our later airport in Beijing is larger, its design can be seen as an evolution of our reinvention of the airport pioneered by Stansted and Hong Kong. Its significance is greater than it physical size. So, yes, without doubt I consider [HKIA] one of the seminal projects of my career."

Today Foster + Partners is working on Mexico City's new international airport, a project it says once again "revolutionises airport design" - the entire terminal being enclosed within a continuous lightweight gridshell, embracing walls and roof in a single, flowing form, evocative of flight.

With an ambition to be the world's most sustainable airport, the compact, single terminal uses less materials and energy than a cluster of buildings, and is easy to navigate, avoiding the need for passengers to use internal trains or underground tunnels.

The challenges of every climate and airport location are unique, Foster says.

In Hong Kong, the building had to withstand typhoons - so the engineers developed an innovative wishbone suspension joint to connect the walls to the roof, a "multidirectional triangle of steel, inspired by a 1930s racing car".

In Mexico, the main challenge is the soil conditions, because the site used to be a shallow lake (so its high water content has little capacity to support large loads). There is also seismic activity in the area.

The airport's superstructure is therefore designed for lightness and flexibility, Foster says. "The roof is a series of interlocking shell structures that resist their loads through in-plane forces, rather than bending, and are thus extremely lightweight. This roof is constructed as a steel space frame, which lands at individual points. It is inherently flexible, which makes it more forgiving of ground movement than a more rigidly supported structure. The structural steel floor system is also lighter than a pure reinforced concrete alternative."

While the technical challenges may differ and technology has advanced in the 17 years since HKIA opened, Foster says the basic aim remains "to make the experience for passengers comfortable, easy, joyful and uplifting to the spirit; [and] to create a gateway that is appropriate to the capital city and the nation which it opens up to".

Boston-based architect Moshe Safdie likens the desire to have big and beautiful airports to the great train stations that defined the Victorian era. However, the race to build highly symbolic aviation gateways is largely the domain of up-and-coming nations: "It's not a worldwide trend - airports in the US are dismal," he says. "But certainly [we're seeing it] in emerging cities of the world, not only in Asia."

His firm, Safdie Architects, is building a major new addition to Singapore's Changi Airport, to be known as Jewel. Housed under a soaring glass dome, Jewel will encompass a total gross floor area of about 134,000 square metres and feature an expansive garden, cabin hotel, restaurants, and attractions in addition to its facilities for airport operations. Centrepieces of the project are Forest Valley, an indoor landscape of trees, palms, and ferns with walking trails; and Rain Vortex, a 40-metre waterfall cascading from an oculus at the top of the glass dome.

Says Safdie: "Our goal was to bring together the duality of a vibrant marketplace and a great urban park side-by-side in a singular and immersive experience. The component of the traditional mall is combined with the experience of nature, culture, education, and recreation, aiming to provide an uplifting experience."

Jewel is slated for completion at the end of 2018.

Mega airport projects are not a trend, but a necessity for today's major cities, according to Zaha Hadid Architects, which is collaborating with French airport engineering specialist ADP Ingeniérie on Beijing's new airport at Daxing.

"Reliable, convenient global connectivity is indispensable for the social and economic vitality of major cities," says Cristiano Ceccato, the project director at Zaha Hadid Architects. "We must also consider that a very significant percentage of passengers will actually use these new airports as hubs - not gateways. They will transfer between flights and never leave the airport. Therefore, we must design passenger user-friendly terminals that accommodate transferring passengers."

Beijing's second airport is planned as one of the world's largest, eventually having seven runways with capacity for more than 100 million passengers a year. Yet its design is compact, reducing the distance between check-in and gate, and between gates for transferring passengers, to no more than 600 metres much less than other global hubs with a large capacity.

Columns in the central atrium are an extension of the terminal's fluid roof structure and extend through every level of the building, uniting all areas of the terminal into a single, continuous space, Ceccato says.

"This one single space makes it easier and quicker for passengers to navigate as they walk through the terminal, yet the fluid formed columns continue the sinuous curvature of the roof and give moments of pause."

Like Foster + Partners' design for Mexico City, Beijing's second international airport will not feature shuttle trains used to ferry passengers at other large airports such as Hong Kong's.

The installation, maintenance and operation of these trains is expensive, and requires constant energy supply," Ceccato says. "It's much more effective to design a terminal that enables people to simply walk shorter distances to everywhere they need to."

Housing so many departure gates in a single building ultimately reduces the carbon footprint of the terminal throughout its construction and then its operational lifetime - further contributing to the required high levels of environmental management and sustainability.

Local flavour is expressed in the symmetry of the design, together with the roof's flowing forms, integrated as a fluid composition that evokes the natural landscapes and principles of traditional Chinese architecture. The colours and materials used express the Chinese traditional visual language.

Chinese influences have captivated Zaha Hadid since the Pritzker Prize-winning British-Iranian architect first travelled to China in 1981, at the beginning of her career, Ceccato says.

"She was intrigued with how traditional Chinese painting layers space into infinity, giving us a sense of depth and progression; how traditional Chinese architecture and garden design integrates and organises the beauty of nature as a sequence of interconnected spaces; and how China's traditional architecture is deeply embedded within the great theatre of Chinese natural landscapes.

"Studying the country's traditional arts, architecture and garden design played an important role in the development of her work and these characteristic principles are evident in the design for Daxing."

Hanging one's hat on a project as prominent as an international airport may be the height of ambition for many architects, but, as Safdie says, it's not about them. Aviation gateways are a matter of national pride and, in Asia, carry great leverage in the race to see which city will be the main hub.

So he expects that the big, the bold and the beautiful will continue to feature in airport design - an architectural speciality for which Safdie predicts "exciting times ahead".