During World War II, the Kallang Airport was the only operational airfield in Singapore capable of supporting Allied campaigns against the Japanese forces.

It was during the Japanese occupation period that the airport's grass landing zone was upgraded into a concrete runway and extended to 5,500 feet (1,700 m).

The structures which were gazetted for conservation by the Urban Redevelopment Authority on 5 December 2008 include the airport's terminal building, administrative blocks, aircraft hangars and control tower.

[10] On 11 February 1930, the Dutch Airline KLM operated the first service flight between Amsterdam and Batavia (now Jakarta), landing at Seletar with a Dutch-made Fokker trimotor monoplane carrying 8 passengers and a cargo of fresh fruit, flowers and mail.

Two years later, in July 1933, Imperial Airways, the flagship airline of the British empire at the time, started a service between London and Darwin via Cairo, Karachi, Calcutta, Singapore and Jakarta.

On 31 August 1931, Sir Cecil Clementi, Governor of the Straits Settlements, announced that Kallang Basin as the location for the new civil aerodrome suitable for land planes and seaplanes, and relieving Seletar of commercial flight activities.

This place was chosen over other possible sites because of its proximity to the city centre as well as its location next to the Kallang Basin, which allowed seaplanes to land.

[12] Positioned at the forefront of aviation innovation, the circular aerodrome's state-of-the-art facilities provided an optimal setting for the airline's operations.

They were joined later by Hawker Hurricanes of 232 Squadron RAF, but attrition took a steady toll on men and machines, and by the last days of January 1942, the airfield had been badly damaged by the bombing and only a small number of aircraft were serviceable.

[13] The growth in aviation traffic was stunted during the war years, a period which saw the landing circle being converted into a single runway to allow use by warplanes.

The PA building held many activities for the ruling People's Action Party, ranging from school visits to social events.

There is a circular glass control tower in the centre, and there are two side blocks, the former terminal building, with an open-air viewing deck on the top floor.

The People's Association kept the concrete structure and transparent glazed walls and repaired the façade, closed the gates, and rebuilt the window on the second floor for reshaping the interior space for the use of offices.