The man who was the structural engineer on Chicago's Sears Tower, once the world's tallest building, paused. He had been asked how he felt the day in 1997 when the Petronas Twin Towers in Kuala Lumpur claimed the title. The pause lengthened. Then John Zils, an associate partner with the international architectural engineering firm Skidmore, Owings and Merrill, let his breath out. 'It's an inevitable thing,' he said from his Chicago office last week. 'It was fine that Sears was the tallest building for 24 years and Petronas came along. But that doesn't matter because there will always be taller buildings.' Last month, those involved in the Petronas Twin Towers, the symbol of Malaysia's economic rise, must have experienced the same feelings of resignation. On October 18, with the instigator of the project, Prime Minister Mahathir Mohamad, about to step aside for his deputy, Taipei 101 in Taiwan was topped out at 509 metres - making it the tallest building in the world. Dr Mahathir was undaunted. 'They have one very tall building, taller than ours, but we have two,' he said. 'We have the distinction of having the tallest twin towers in the world. No one else has that.' One-upmanship is the crux of the tall building game. Mr Zils' firm is now working on what it says will be the world's tallest building in Dubai. Construction has started, but Mr Zils is secretive about how high it will be. The reason is simple - if such information gets out too early, someone else will build a bigger one. In a game where billions of dollars are at stake for the sake of prestige, that is crucial. Builders of the off-again, on-again Shanghai World Finance Centre have similar aspirations. There is talk India wants the title. Two massive buildings are going up in South Korea, either of which could be in the running. East Asia, more than any other region in the world, wants taller buildings. That is despite terrorists crashing two jetliners into New York's World Trade Centre towers on September 11, 2001, toppling the world's third-tallest building. Plans have been announced to regain the title on the site with a new, 541-metre world trade centre, but the reality in the United States is that the desire for skyscrapers and renting office space in them has waned. Mr Zils said that before September 11, Sears Tower was always 100 per cent full, even if elsewhere in Chicago, office space vacancies were 15 per cent or more. 'People want to be located there because it's prestigious to say you're a tenant,' he said of the landmark and popular tourist attraction. Post-September 11, the building was still rented to capacity, but some companies were considering moving when their leases expired. The trend of firms moving out of skyscrapers or renting on lower floors was prevalent throughout the US. Towers were still being built - but they were in the commercially driven, economically sound 50 to 70-storey range. Asia is bucking the trend. In the region, prestige, ego and attracting investors by making a statement take precedence over fears of falling victim to another September11-style attack. Hong Kong - already home to three of the 10 tallest buildings in the world - is eager to stretch its skyline. The Mass Transit Railway Corporation's Union Square Phase 7 in Jordan is projected to be 102 storeys and 480 metres high when completed in 2007. That will be 14 floors and 65 metres more than Two International Finance Centre, known as 2IFC, the city's tallest building and fifth in the world rankings. Another 102-storey building, property developer Chinachem's Nina Tower in Tsuen Wan, was rejected by town planning authorities because it was considered a danger to aircraft using Chek Lap Kok airport. Chinachem is still going ahead with the project, although it is building two shorter towers. Although Hong Kong's lack of space makes for a vertical city, having an office on the top floors of tall buildings is still considered a status symbol - but usually for mainland firms rather than security-conscious foreign ones, experts said last week. Jason Cruz, Hong Kong's associate director of the global property solutions firm Cushman and Wakefield, said there was no shortage of mainland companies with a 'we're here now, we're an international firm' attitude looking for 'flashier' premises. 'All of my clients have been particularly careful with 2IFC, viewing it as a potential high security risk and are basically staying away from it,' Mr Cruz said. 'That hasn't stopped a lot of other companies like Lehmann Brothers, Ernst and Young and Nomura taking space there. But the fact that it is the tallest building has put a lot of people off it,' he said. Constructing buildings for the sake of height is an expensive business. Architectural engineers believe that the optimal economic height of buildings is about 70 floors. Beyond that, the ratio of construction costs versus returns is proportionally less attractive. The main reason is elevators, according to Raymond Wong Wai-man, a lecturer with City University of Hong Kong's department of building and construction. 'Making a very tall building is not very economical in terms of space, construction cost and engineering input,' Mr Wong said. 'Beyond the critical point of up to 60 or 70 storeys, a lot of floor space is lost to elevators. The building supports that make it safe also cost a lot of money.' He said that in East Asia, such considerations seemed to be disregarded for the sake of building a landmark, as with Taipei 101. If developers were wiser, they would come to the conclusion that a super-tall building was not economical. Such views are not wholly shared by the chairman of the Council on Tall Buildings and Urban Habitat, Ron Klemencic. As the keeper of the list of the world's tallest buildings and the rules determining which ranked, he is passionate about the phenomenon. Apart from charging a premium for higher floors, lucrative earnings could be made by putting communications equipment on the top of tall buildings and attracting broadcasters, he suggested. But he agreed with Mr Wong's assessment of why Asian companies had surpassed the developed world in their lust for higher buildings. 'The incentive with super-tall buildings in Asia - whether it's a country like Malaysia or a commercial group that's trying to call attention to its rising world presence - is that it sends a very loud signal, whether you're claiming to be, or are, the tallest building in the world,' Mr Klemencic said from his office at the Seattle structural engineering firm Magnusson Klemencic Associates. 'It draws a lot of attention and a lot of tourist traffic just for being there.' Because of the stakes, pride is also an issue. In Hong Kong, 2IFC and Central Plaza both claim to be the tallest. A similar row raged between Sears and Petronas - prompting the Council on Tall Buildings to produce an official definition of tallness. Mr Klemencic said the debate centred on the spires and pinnacles architects sometimes topped buildings with. 'The salient issue in terms of the definition of height is the distance from the main entrance of the building to the top of the architecture,' he said. 'Therein lies the subjective debate - where is the top of the architecture? The test is if you could take whatever is on top of the building and snap it off, does the building look the same?' The council, using this logic, determined that the Petronas Twin Towers were taller than Sears Tower. Then there is the council's rule that the majority of the space created by a building has to be occupied for commercial or residential use. Taipei 101 will not be open for business for another year, so has not yet made the council's list of tallest buildings. That is not the view of Taipei's citizens, who can see the structure from anywhere within the city. Mr Klemencic hinted that a council meeting on the subject may soon reconsider the rule. For highly wealthy companies wanting to make a billion-dollar statement, getting on the list is all-important. But observers agreed that, ultimately, the race for the sky was about making money. In developing Asian countries such as China, where 8 per cent-plus growth rates mean a lot of companies are fighting for supremacy, being at the top of the heap is being taken in a highly literal sense.