CONGESTED terminals and flight delays will become common for more travellers if airports do not move urgently to build new infrastructure, a global airline body has warned.
Passenger terminals at several major airports in Asia, including those in Bangkok, Hong Kong, Beijing, Jakarta and Hanoi, are already full, the International Air Transport Association (Iata) said.
This means that the facilities are handling the maximum number of air travellers and, in many cases, more in a year than they were designed to process.
The result is a poor experience for travellers, with crowded terminals and long queues at immigration and other areas.
Based on past traffic trends and future projections, airports in Manila, Incheon and Dubai will hit full capacity either this year or next, said Iata director for airports and fuel Hemant Mistry.
Globally, close to 230 airports - up from 90 now - are expected to run out of space at their passengers terminals by 2020, said Mr Mistry.
By then, more than 60 airports, from just six now, will be operating their runways at almost full capacity.
He said: "The propensity to travel has continued to grow but the building and updating of aviation infrastructure have tended to fall behind and, in some cases, stagnate."
The other problem is a lack of proper planning and coordination, he added.
"There is no point in landing more aircraft on a new runway if there is nowhere to park these same aircraft at the air terminal," he said.
To handle more flights, airports can either build more runways or operate existing ones more efficiently.
Airports can also look to better train air traffic controllers.
In Asia, the Iata expects the demand for air travel to grow by 4.9 per cent annually - higher than the global rate of 4.1 per cent - over the next two decades.
There is an urgent need for airports in the region to tackle infrastructure challenges, said Mr Vinoop Goel, the association's Asia-Pacific regional director for airports, passengers, cargo and security.
"Some like Singapore and Hong Kong are more proactive. Kuala Lumpur and Thailand struggled a bit but seem to have got their act together now. South Korea is well ahead of the game.
"Jakarta has looked at multiple proposals over the years and is finally focusing on expanding the current airport in Jakarta.
"Sydney is looking at a second airport and China has plans for Beijing II," he said.
Changi Airport's three passenger terminals and runways are expected to run out of capacity in 2018.
By then, however, Changi is likely to have opened Terminal 4 and expanded Terminal 1. This will increase its handling capacity from 66 million passengers a year now to 85 million passengers.
Changi has also partnered British air traffic management firm Nats, which manages flight movements at Heathrow - one of the world's busiest airports - to
increase the number of flights that the Singapore airport can handle.
Ultimately, there is no "magic number" when it comes to how big an airport terminal should be or how many runways it needs, said Mr Goel.
"It is up to each airport to decide where the sweet spot is in terms of efficient use of resources ... and the level of service it wants to offer to travellers."
He added that the focus needs to be on cost efficiency, and airports should optimise the throughput of their existing infrastructure.
"You want to build ahead of traffic growth but you also do not want a white elephant," Mr Goel noted.
"This is where the challenge lies and, in the end, travellers will decide which airport has got it right."