Why do we believe we need a third runway at the Hong Kong International Airport? It's important to frame the debate through the prism of Hong Kong's place in world. That means a focus on three key contexts:

The airport has been a fabulous success story and will reach capacity saturation 15 to 20 years before the original forecast date of 2040. We should invest on the back of that success.

Aviation is the foundation on which the four pillars of Hong Kong's economy - finance, trade and logistics, tourism and professional services - are built. These are international, not domestic, industries that rely heavily on our connectivity to the rest of the world.

It has taken more than a decade to achieve the critical mass needed for Chek Lap Kok to become Asia's premier aviation hub. We have many regional competitors ready to take that mantle if we let it slip.

That's the big picture. And as a key driver of our economy, aviation is at the core of that big picture. The industry supports more than 260,000 jobs, or over 7 per cent of the total working population and accounts for 8.2 per cent of our gross domestic product, according to a Chinese University of Hong Kong study.

These facts speak for themselves.

The four pillars of our economy will be at risk if we don't have the future runway capacity at Chek Lap Kok to leverage our superb location at the heart of Asia and our unrivalled access to the mainland market.

The Airport Authority's master plan to 2030 spells out with great clarity the challenges facing the airport if long-term growth is constrained. It rightly says Hong Kong would begin to lose its status and competitiveness as an international business centre and aviation hub.

Are there alternatives to a third runway? One option is to nip and tuck around the edges with the existing two runways. Frankly, this option only buys us a couple more years of growth and then we run into constraints again. The great artery that is our aviation hub would then still clog up and no amount of bypass surgery will fix it. And that would mean a slow choking of the lifeblood of our economy, with the resulting loss of growth, opportunities and jobs.

It has been suggested that we collaborate with one or more of the other four airports in the Pearl River Delta to obviate the need for a third runway. One idea is to split 'duties' between two airports - Hong Kong handling long haul, Shenzhen handling domestic flights with a rail link connecting the two airports. A great idea on paper that just won't work.

As David Dodwell pointed out on this page last week, experience around the world shows that passengers simply do not like inter-airport transfer. And why should they when they can be served by a single, magnificent airport like the one we have in Hong Kong?

Attempts to link airports elsewhere in the world - even two airports within the same metropolitan area - have not been successful.

In London, Heathrow and Gatwick do not operate as one airport and transfer traffic between the two is almost non-existent. In the United States, New York, Chicago and San Francisco have been unable to generate transfer traffic between the major airports in each city. And closer to home in Japan, Haneda and Narita airports do not support each other. There is not a single example anywhere in the world where a two airport 'link-up' has worked.

In any event, Shenzhen airport's second runway is due to open later this year but, even with this additional runway, it will face capacity constraints around the same time that our own airport reaches a bottleneck. So it's not a starter, either.

As a major international financial centre, trade and logistics hub and prime travel destination, Hong Kong needs to have its own airport with long-term capacity to keep us ahead of the game. And while our aviation hub might be winning the race now, our competitors will gallop past us if we don't keep up the pace. We need to invest on the back of the spectacular success of our aviation hub by growing it, not stifling it. That way enables us to seize the opportunities so uniquely provided to us by our special relationship with China and our strategic location at the heart of Asia. If we don't grasp this great opportunity, the only people celebrating will be our rivals in Singapore, Seoul, Taipei and Bangkok.

John Slosar is chief executive of Cathay Pacific Airways