The Japanese and U.S. governments have agreed to lower the minimum altitude for low-level flight training by the U.S. Marine Corps' MV-22 Osprey transport aircraft in mountainous areas to about 60 meters from around 150 meters.
The agreement was announced by the Defense Ministry. The change, slated to take effect Monday, will not apply to areas in Okinawa Prefecture.
Japan's aviation law sets the minimum safe altitude for aircraft at 150 meters in uninhabited areas.
While U.S. military aircraft are not covered by the law, the Japanese and U.S. governments agreed in 2012 that MV-22 Ospreys would be operated at altitudes of 150 meters, or about 500 feet, or more in principle.
The low-altitude flight training is conducted on fixed-wing mode, in which the Ospreys' rotors are oriented horizontally, in mountainous areas without houses. The fixed-wing mode is a technique necessary for avoiding detection by enemy radars and attacks with anti-air weapons and for conducting search and rescue operations.
The Marine Corps has deployed 24 MV-22 Ospreys at its Futenma Air Station in the Okinawa city of Ginowan.
At a "two-plus-two" meeting among their foreign and defense ministers in January, Japan and the United States confirmed "steady progress" in the implementation of "realistic training and exercises" such as MV-22 Ospreys' low-altitude training.