The U.S. Marine Corps started low-altitude training flights for tilt-rotor Osprey aircraft in Shikoku and in Wakayama Prefecture on Wednesday. It is regrettable that the United States notified Japan about the training route only shortly before the flights began.

The training flights, scheduled to end today, are the first to be conducted over the main islands of Japan since the U.S. first deployed the aircraft at U.S. Marine Corps Air Station Futenma on Okinawa Island in October over strong local opposition.

It is expected that the U.S. Marine Corps will repeat Osprey training flights every month along various routes over the main islands of Japan. The U.S. should not try to establish faits accomplis of Osprey training flights without providing sufficient information to Japan with regard to such flights.

Communities along the routes are very apprehensive about the Osprey’s safety. Any attempt to expand training flights unilaterally will only increase public opposition.

On Monday evening, the U.S. Forces Japan notified the Japanese Defense Ministry that the Marine Corps would carry out the current training flights using the “Yellow Route” over mountainous areas of Oita, Fukuoka, Kumamoto and Miyazaki prefectures in Kyushu. The next day, the Marine Corps suddenly changed the schedule; the U.S. side told the ministry that the flights would use the “Orange Route,” which runs east and west from Wakayama Prefecture in Honshu to Tokushima, Kochi and Ehime prefectures in Shikoku.

Three Futenma-stationed Osprey aircraft that were temporarily moved to U.S. Marine Corps Air Station Iwakuni, Yamaguchi Prefecture, are taking part in the training flights.

The U.S. side explained that the sudden schedule change was due to firing practice by the Japanese Ground Self-Defense Force on the Hijudai training area in Oita Prefecture. Coordination between the U.S. side and the Defense Ministry seems lacking. The U.S. has not disclosed detailed information about the flights.

Under a Japan-U.S. accord, Osprey aircraft must fly at an altitude of 150 meters or more during the day and 300 meters or more at night. Since the aircraft weave through confined valleys during training to avoid detection by radar, risks are higher than for ordinary flights. Night flights heighten the risks. Local residents are likely to feel that their safety has been ignored.

Lack of information only adds to the worries. The government should have the U.S. Forces Japan provide detailed information on when, where and how Osprey aircraft will fly. It also must make sure that the aircraft will not violate the safety accord including provisions that prohibit flights over historical sites, nuclear power plants, schools and hospitals.

The central and local governments must strictly monitor the Osprey flights, checking such factors as flight altitudes, noise levels and flight modes, and then publicize the monitoring results. For this monitoring to become possible, disclosure of detailed information from the U.S. side will be indispensable.