The government has received approval from the United States to set new commercial flight routes in U.S.-controlled airspace over Tokyo’s Haneda airport in order to increase services ahead of the 2020 Olympics, government sources said Tuesday.

The U.S. has controlled huge areas of airspace over the capital and vicinity since the end of World War II. Tokyo will explore whether the latest move could eventually lead to Washington formally returning more of the airspace, the sources said.

The so-called Yokota Rapcon airspace is set in six different levels at altitudes between 2,450 and 7,000 meters, stretching over Tokyo and eight other prefectures. Yokota is the name of the air base in western Tokyo where the U.S. military in Japan has its headquarters.

Airspace restrictions have forced many commercial flights using Haneda to detour or fly higher, causing air traffic congestion.

The government plans to expand annual arrival and departure slots at Haneda by up to 39,000 in time for the 2020 Tokyo Games from the current 447,000. It has also drawn up four new routes, three of which can go through the U.S.-controlled airspace.

The new routes will boost the airport’s landing and departing capacity as they would allow two airplanes to land simultaneously on two runways, the sources said.

The United States, in working-level negotiations, has already approved the use of the three routes to be set in its airspace, the sources said.

The airspace has been under U.S. military control since August 1945, when the U.S.-led Occupation took over the country’s flight control operations. Parts of the airspace were returned in 1992 and 2008.

The Yokota radar approach control covers airspace above Tokyo, Tochigi, Gunma, Saitama, Kanagawa, Yamanashi, Niigata, Nagano and Shizuoka prefectures.