Changi Airport could run out of space a few years after its fifth and largest terminal opens by the end of the next decade, an aviation consultancy has predicted.
By the time Terminal 5 is up and running, Changi will be able to handle up to 135 million passengers a year - up from 66 million now.
The additional capacity could be fully utilised by 2032 or even earlier, according to leading industry consultancy OAG, which has for the first time done a detailed analysis on Changi's growth prospects.
The forecast is based on past traffic patterns, plans by home carrier Singapore Airlines (SIA) and developments in the region.
On the surface, the case for a doubling of traffic seems less strong than it might have been a few years ago, the report noted.
Singapore's position as a stop- over destination for long-haul travellers, for example, has been challenged in recent years by rival airport hubs, in particular, Dubai.
Qantas' decision in 2013 to move its hub for Australia-Europe flights from Singapore to Dubai, for example, has reduced Changi's share of the market.
Other trends, though, suggest that there is much for Changi to look forward to, OAG noted.
In the last 10 years, passenger traffic at the airport increased by an average of 5.5 per cent a year.
Between January and June this year, growth was much higher at 8 per cent, with a total of 28.8 million passengers handled. China, Malaysia, Thailand and Vietnam were the top markets with double-digit increases in passenger traffic.
Despite the slowdown in long- haul traffic, the Singapore airport is taking advantage of strong growth in the region.
A third of routes in and out of Changi is under 3,000km - approximately four hours of flight time.
At the other end, the proportion of routes above 6,000km has fallen from 13 per cent in June 2010 to 11.3 per cent in June this year.
The demand for air travel in the region is expected to be strong in the coming years, said Mr Mark Clarkson, OAG's Asia-Pacific business development director.
Huge aircraft orders by Asian carriers will support the growth, he told The Straits Times.
Malaysian budget carrier group AirAsia, for example, has an outstanding order of close to 250 planes, while India's IndiGo has ordered more than 220.
Growth plans by the SIA group, comprising the premium parent carrier, regional arm SilkAir as well as budget carriers Scoot and Tigerair, will also boost passenger traffic at Changi Airport, OAG said.
The forecast is sound, said Mr Kent Yar, deputy managing director and global head of aerospace at Morgan Philips Executive Search. But future decisions on whether capacity needs to be boosted beyond 135 million a year must take into account different factors, he said.
For example, planners would need to determine if the demand is short term - due to low oil prices that would stimulate the industry, for instance - or more long term.
Apart from a physical expansion, increasing productivity through technology and automation can be used to beef up handling capacity, he said.
Even as the future looks bright, there are no growth guarantees, said Singapore Management University Assistant Professor Terence Fan, who specialises in transport.
Key questions include how the global economy will grow in the next decade and how Asean will develop, he added.
Mr Yar said: "In the event that there is instability within the region, we will see a decline in terms of travellers."
Other factors can also impact demand. For example, a spike in oil prices would hit airlines and eventually result in higher airfares, dampening travel demand, he said.