Tokyo was formally notified on Thursday of a planned fleet upgrade that would replace aging CH-46 helicopters with the Osprey, which the Marine Corps formally designates MV-22 and the Air Force CV-22.

The Pentagon said the MV-22 aircraft had an excellent safety record based on more than 115,000 flight hours including combat, humanitarian assistance, training and test and evaluation missions.

Basing the Osprey in Okinawa will strengthen significantly U.S. ability to provide for the defense of Japan, perform humanitarian assistance and disaster relief operations and fulfill other alliance roles, it said.

The United States and Japan announced in April a revised agreement on the footprint in Okinawa that would shift 9,000 Marines from there to Guam and elsewhere in the Asia-Pacific, including Hawaii and Australia.

Okinawa was occupied by the United States from 1945 to 1972. It accounts for less than 1 percent of Japan’s soil but hosts three-quarters of the U.S. military facilities in the country by land area.