Plans to build a new runway at Tokyo’s congested Haneda Airport later this decade could affect flight patterns at Yokota Air Base, the hub of U.S. military air operations in mainland Japan.

Japanese government planners will ask the United States to consider altering the boundaries of U.S.-controlled airspace near Tokyo to maximize the capacity of a new runway planned at Haneda Airport, according to Land, Infrastructure and Transport Ministry officials.

Aimed at increasing the number of takeoffs and landings at Haneda to 40 per hour from the current 28, the plan was revealed at a recent meeting with leaders of towns near the airport.

Yokota Air Base is 28 miles west of downtown Tokyo and about 31 miles west of Haneda Airport.

The new runway, to be completed in 2009, would alter Yokota’s airspace boundaries.

“Basically, aircraft routes avoid Yokota airspace,” a ministry spokesman said. “To handle increased numbers of takeoffs and landings at Haneda, there is a need to look over routes.”

The new runway also would require an additional flight path over the sea, the ministry said, to minimize jet engine noise over urban areas.

However, when the United States and Japan will discuss the issue remains uncertain.

“We haven’t been approached by the government of Japan as of yet,” Capt. Richelle Dowdell, 5th Air Force spokeswoman at Yokota, said Wednesday. “It’s difficult to address the topic since there’s been no official request; we don’t want to speculate on what needs to be done.”

The U.S. military returned about 10 percent of Yokota’s airspace in 1992, giving Japanese air traffic controllers sole jurisdiction over civilian aircraft on westward-bound flights departing Haneda.

The additional runway will see Haneda’s commercial air operations increase from 270,000 to 407,000 flights annually, according to the ministry’s Air Traffic Services System Planning Division.

A ministry spokesman said drilling is to begin in an area marked for the new runway as a pre-environmental assessment soon after the Japanese Diet, or parliament, passes the budget for the new fiscal year.

Yokota’s airspace covers some 8,500 square miles over Tokyo and eight prefectures. It includes areas north to Niigata and south to Kanagawa prefecture, including Izu Peninsula.

Controllers with Yokota’s radar approach control work closely with the Tokyo area control center, which provides air traffic control service to commercial and general aviation operating in the region.

Civilian aircraft may pass through Yokota-controlled airspace, but only under the guidance of that base’s Air Force controllers.

At times, U.S. control of airspace has sparked friction with Japanese government officials. In 2001, for instance, a Japan Air Lines DC-10 nearly collided with a JAL B-747 over Shizuoka prefecture. The planes carried more than 700 passengers and crew members. Forty-two B-747 passengers were injured when the pilot took evasive action to avoid a collision.

Tokyo’s Gov. Shintaro Ishihara blamed Yokota airspace restrictions for the near miss. Japan’s Aircraft and Railway Accident Investigation Commission, however, concluded that Japanese air traffic controllers provided wrong flight altitude numbers to the pilots after telling them to change course.

Both pilots chose to follow air traffic control advice instead of the computerized Traffic Alert and Collision Avoidance System (TCAS) aboard their aircraft, which warned of an impending crash. The planes came within 180 feet of each other.

To prevent similar incidents, the commission recommended that the International Civil Aviation Organization instruct pilots to give priority to computerized warnings over controllers’ verbal instructions.

For several years, the United States and Japan have discussed returning airspace now controlled by U.S. Forces on Okinawa, but no decisions have been made.

— Hana Kusumoto contributed to this report.

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