Now, air traffic controllers at busy Changi Airport have to physically see the planes from a control tower to guide all flights landing and taking off.

But video and display technology has advanced to such a point that air traffic controllers can, in the future, guide planes from a windowless room.

When the technology is put in place in the coming years, Changi is set to be the first major airport in the world to be equipped to do this, Civil Aviation Authority of Singapore director-general Kevin Shum told The Straits Times.

"Smart tower technologies can help us better manage Changi's increasing air traffic, thereby reducing delays for passengers and saving fuel for airlines. We are excited by the possibilities and will invest in the necessary research and development," he said.

The plan is to retain the physical control towers to complement the remote operations.

The need to better manage flights and integrate operations across several runways and terminals will be critical as the airport continues to expand.

With Terminal 4 set to be launched later this year and Terminal 5 slated to open in phases from the end of the next decade, Changi is looking at more than doubling its current handling capacity to about 135 million passengers a year.

Last year, a record 58.7 million passengers passed through Changi's gates.

Research into smart solutions for air traffic management is a focus for many growing airports, said Ms Juliana Goh, head of research at Mitre Asia Pacific Singapore, a not-for-profit company headquartered in the United States that conducts research in various fields, including aviation.

In December 2014, Amsterdam's Schiphol airport became one of the first to test a remote runway surveillance system to monitor air traffic.

But Ornskoldsvik, a small airport in Sweden, is the first airport in the world where all flights are controlled remotely. Planes taking off or landing there are guided by air traffic controllers who are located nearly 170km away in the town of Sundsvall.

Other countries looking at remote towers include Hungary, Britain, the US and Germany.

Ms Goh said video and display technology has advanced to the point where clear images can be captured and displayed to air traffic controllers.

On whether there are safety concerns in implementing the system at busy airports like Changi, she said: "As with any introduction of new technology into a safety-critical system, operational acceptance by air traffic controllers is key."

She added: "In the case of remote towers, the fundamental issue for the controller is: 'Can I trust what I see on the video feed? Can I still see what I need to see to do my job safely and efficiently?'

"Demonstrating to the controller that these two objectives can be met by the technology is essential to successful operational acceptance."

Ultimately, air traffic service providers will have to demonstrate that there is an equivalent level of safety when comparing a physical tower with a remote one, she said.

Redundant systems and operational procedures will also need to be in place to mitigate the effects of camera or system failures, noted Ms Goh.

The progress made so far "gives the industry confidence that operating remotely, full time, for a major airport is within reach", she said.