When Kansai International Airport (KIX) opened in Japan in 1994, it was considered an engineering marvel. It is one of the floating airports in the world, and its construction cost is about 20 billion dollars.
30 years later, it remains an important center in Japan.
In 2022, Statista ranked KIX as the third busiest airport in the country, after Narita International Airport (NRT) and Tokyo Haneda Airport (HND).
The airport serves as a hub for major airlines including All Nippon Airways, Japan Airlines, Air Nippon Cargo Airlines and even Japanese low-cost carrier Beach.
But experts are now sounding the alarm:
– KIX Airport could be completely underwater by 2056, he wrote Aviation.
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Osaka Bay. Below is the floating Kansai International Airport, which is sinking more quickly than experts expected. Photo: Yujun3/Shutterstock/NTB
Built as a replacement
Kansai Airport was built to relieve congestion at Osaka's first airport: Itami Airport (ITM).
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The original Kansai site was envisaged to be near the Kobe region of Japan, but city officials and local residents protested the plan.
Instead, the authorities decided to build the new airport in a unique location – in the middle of the sea, where operations could take place 24 hours a day without disturbing local residents.
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To build an airport in the middle of the sea, engineers drained millions of liters of water from the 20-metre-deep soft clay that lies below the current site of the airport, before building a wall towards the sea.
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The reclaimed land was like a wet sponge, but it turned into a dry, dense foundation to bear the weight of the airport buildings.
Construction crews placed a five-foot-thick layer of sand on top of the clay layer, then installed 2.2 million vertical pipes, each about 16 inches in diameter. These tubes were then pounded into clay and filled with sand and soil to create a more stable base.
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Kansai International Airport, Osaka, Japan Photo: Flyde Esugei/Shutterstock/NTB
Seven years of construction time
Construction of KIX Airport began in 1987 and took seven years to complete.
For 30 years, the floating airport withstood a major earthquake in 1995. The Great Hanshin Earthquake measured 7.2 and killed more than 6,000 people.
In 1998, the airport also survived Hurricane Stella, which caused more than 70 landslides.
It was known that the airport would sink due to the ground. But it is declining faster than expected. In 1990, it was estimated that the “fungal” foundation would cause the airport to sink by 5.7 metres.
It's more dramatic:
In a 2018 Smithsonian Magazine interview, Aero Time quoted Yukako Handa, a Kansai Airports representative, as saying:
“When Kansai Airport was built, the amount of soil needed to reclaim the land was determined based on the required ground level and estimated subsidence over 50 years after construction.
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By 2018, the airport had fallen 38 feet (11.5 metres) since its construction, 25% more than experts had predicted.
But the Japanese are optimistic and believe the outlook is still positive. The airport continued to expand.
In December 2023, a new international departure area was opened. Future expansions are scheduled to be completed by 2025.
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