In the 1960s, when the Kansai region was rapidly losing trade to Tokyo, planners proposed a new airport near Kobe and Osaka. The city's original international airport, Itami Airport, located in the densely populated suburbs of Itami and Toyonaka, was surrounded by buildings; it could not be expanded, and many of its neighbours had filed complaints because of noise pollution problems. Expansion at Itami was also constrained by geography, because the airport was surrounded by mountainous terrain; offshore construction therefore became the practical alternative.

After the protests surrounding New Tokyo International Airport (now Narita International Airport), which was built with expropriated land in a rural part of Chiba Prefecture, planners decided to build the airport offshore. The new airport was part of a number of new developments to revitalize Osaka, which had been losing economic and cultural ground to Tokyo for most of the century.

Initially, the airport was planned to be built near Kobe, but the city of Kobe refused the plan, so the airport was moved to a more southerly location on Osaka Bay. The offshore location allowed 24-hour operation, unlike its predecessor in the city.

Construction

An artificial island, 4 km (2+1⁄2 mi) long and 2.5 km (1+1⁄2 mi) wide, was proposed. Engineers needed to overcome the extremely high risks of earthquakes and typhoons (with storm surges of up to 3 m or 10 ft). The water depth is 18 metres (59 ft) on top of 20 metres (66 ft) of soft Holocene clay which holds 70% water. A million sand drains were built into the clay to remove water and solidify the clay.

Construction started in 1987. The sea wall was finished in 1989 (made of rock and 48,000 tetrapods). Three mountains were excavated for 21 million cubic metres (27 million cubic yards), and 180 million cubic metres (240 million cubic yards) was used to construct island 1. Over three years, 10,000 workers using 80 ships took 10 million man-hours to complete the 30-or-40-metre (100 or 130 ft) layer of earth over the sea floor and inside the sea wall. In 1990, a three-point-seven-five-kilometre (2.33 mi) bridge was completed to connect the island to the mainland at Rinku Town, at a cost of $1 billion. Completion of the artificial island increased the area of Osaka Prefecture just enough so that it is no longer the smallest prefecture in Japan (Kagawa Prefecture is now the smallest).

The bidding and construction of the airport was a source of international trade friction during the late 1980s and early 1990s. Prime Minister Yasuhiro Nakasone responded to American concerns, particularly from Senator Frank Murkowski, that bids would be rigged in Japanese companies' favour by providing special offices for prospective international contractors, which ultimately did little to ease the participation of foreign contractors in the bidding process. Later, foreign airlines complained that two-thirds of the departure hall counter space had been allocated to Japanese carriers, disproportionately to the actual carriage of passengers through the airport.

The island had been predicted to sink 5.7 m (18 ft 8 in) by the most optimistic estimate as the weight of the material used for construction compressed the seabed silts. However, by 1999, the island had sunk 8.2 m (26 ft 11 in) – almost 50% more than predicted. The project became the most expensive civil works project in modern history after twenty years of planning, three years of construction and US$15bn of investment. Much of what was learned went into the successful artificial islands in silt deposits for New Kitakyushu Airport, Kobe Airport, and Chubu Centrair International Airport. The lessons of Kansai Airport were also applied in the construction of Hong Kong International Airport.

In 1991, the terminal construction commenced. To compensate for the sinking of the island, adjustable columns were designed to support the terminal building. These are extended by inserting thick metal plates at their bases. Government officials proposed reducing the length of the terminal to cut costs, but architect Renzo Piano insisted on keeping the terminal at its full planned length.

The airport's opening date was decided by the Ministry of Transportation in 1993, mainly to avoid confusion among airlines, airports, and travelers during the peak July-August travel season.

The construction of Kansai International Airport received much attention from local newspapers, particularly Osaka editions of major national newspapers, than those of Tokyo.

Just before the airport was opened, the Ministry of Transportation approved the landing fee for its international flights at 2400 yen a tonne.

The airport was opened on 4 September 1994, being the first in Japan to operate 24 hours a day.