Earlier this month, the Hong Kong International Airport celebrated its fourth birthday. By most standards, the first four years of the facility's life have been spectacularly successful. In spite of a disastrous opening for its cargo operations - computer glitches meant chaos for several weeks upon the switch being thrown - Chek Lap Kok remains the busiest air-freight centre in the world. It is also the busiest passenger airport in Asia, ahead of Tokyo-Narita and Bangkok. Of the top 50 busiest airports in the world in 2000, Chek Lap Kok ranked twenty-second, according to Airports Council International. By comparison, Singapore's Changi International Airport trailed a distant thirtieth. The Airport Authority pins its success on a number of factors, including Hong Kong's wealth of connecting destinations both internationally and in China. That half the world's population is within five hours' flight away is a popular refrain from the authority. Realistically, the reason for Chek Lap Kok's success - and that of the old Kai Tak airport - is simple. Without China, in particular the Pearl River Delta, Hong Kong's economic potential, and hence its airport, would be little better than that of a handful of contenders across the region. India, for instance, offers Hong Kong an equally large catchment population as China, but few would argue that the sub-continent was a driver for the SAR's growth. The biggest part of Chek Lap Kok's success derives from the SAR's proximity to Guangdong province, which has emerged over the past two decades as, arguably, the world's most important manufacturing and production centre. About 33 million passengers came through Chek Lap Kok last year. Of those passengers, 41 per cent used Hong Kong as a transfer point to and from other destinations. Again, of the total, 18 per cent were from the mainland, while another 20 per cent of passengers using Chek Lap Kok originated from Taiwan. At least 40 per cent of this Taiwanese traffic, if not more, was believed to be bound for the mainland. Indeed, opportunities arising from the continued growth of the mainland economy and relaxation of travel restrictions for Chinese citizens are mentioned time and again in the Airport Authority's latest annual report as the biggest driver for future expansion. But despite the optimism, the focus on China is precisely the point at which problems arise. While the airport was being conceived and designed about 15 years ago, few people could have foreseen the type of traffic growth that awaited Chek Lap Kok. In the early days, airport planners believed that Hong Kong would remain a major destination in its own right, with Chek Lap Kok serving as a focus point for heavy jetliners from the United States and Europe. The planners also envisaged the airport as a major sixth-freedom hub. That is, frequent and sufficiently large flights of perhaps 150 to 200 passengers and assorted cargo from secondary cities in the region, such as Taipei, Bangkok and Manila, would land in Hong Kong to connect to major trunk routes to take advantage of the concentration of international traffic in the SAR. Indeed, the modular design of the airport terminal building meant that gates in the main terminal building could be repositioned with ease to accommodate the next generation of super jumbo jets, such as Airbus A380, that are expected to ply those trunk routes. While the early assumptions of Chek Lap Kok's planners remain valid to some degree, almost no one expected the rapid rise of China as a major aviation market. And, to be fair, even fewer people in the industry believed that the mainland would become such a critical component of Hong Kong's growth. But the downside of China's increased influence is that the mix of aircraft prevalent at Chek Lap Kok will increasingly lean towards smaller sub-100-seat aircraft. While a large proportion of mainland traffic will still congregate on the core routes between Beijing, Shanghai and southern China (which includes both Hong Kong and Guangzhou, with its own impressive facility), the growth to take place will be on the smaller routes to third-tier cities across China. According to the 1990 census, China already had 99 cities with a population of more than one million. The authority acknowledges the beginnings of a problem. While aircraft movements rose nearly 6.5 per cent last year, passenger throughput fell more than 2 per cent. This trend can only be expected to intensify. As such, if China-focused growth is to take place to the extent that the authority hopes it will, there is significant doubt over whether Chek Lap Kok can ever come close to utilising its 87-million-passenger design capacity. For a facility that cost HK$55 billion to build just four years ago, that is a significant lack of foresight in the government's planning. Even more amazingly, for a public investment of such immensity, the original plans make no allowances for contingencies in case of deviations from the government's original business plan for the airport. As a result, the authority has had to go hat in hand to Legco with a new plan to allow it to extend its operations to other parts of Hong Kong and China. So, in spite of the relative success of its first four years, the authority would be wise to ensure that the next four are better thought out. Happy birthday, Chek Lap Kok.