Singapore Changi Airport (IATA: SIN, ICAO: WSSS) is the primary civilian airport in the Republic of Singapore, and one of the largest transportation hubs in the world. Singapore’s International Airport at Paya Lebar, Singapore’s third main civilian airport after Seletar Airport (main airport from 1930 to 1937) and Kallang Airport (1937–55) opened in 1955 with a single runway and a small passenger terminal. With growth in global aviation transport, the airport was facing congestion problems. Its inability to cope with the rising traffic became critical by the 1970s; annual passenger numbers rose dramatically from 300,000 in 1955 to 1.7 million in 1970 and to 4 million in 1975.

The government had two options: expand the existing airport at Paya Lebar or build a new airport at another location. After extensive study, a decision was made in 1972 to keep the airport at Paya Lebar, as recommended by a British aviation consultant. Plans were made for the building of a second runway and an extensive redevelopment and expansion to the passenger terminal building. A year later, however, the plans were reviewed again as the pressure to expand the airport eased because of the 1973 oil crisis. Concerned that the existing airport was located in an area with potential for urban growth, which would physically hem it in on all sides, the government subsequently decided in 1975 to build a new airport at the eastern tip of the main island at Changi, at the existing site of Changi Air Base, where the new airport would be easily expandable through land reclamation.

Each week, about 6,800 flights land or depart from Changi airport, with more than 55 million passengers passing through the airport a year.