Japan has suspended flights by its Osprey aircrafts, officials said.

It comes the day after a US air force Osprey based in Japan crashed into the sea during a training mission.

Tokyo has also asked the US military to ground all Ospreys operating in Japan except for those searching for victims of the crash.

A senior defence ministry official, Taro Yamato, told a parliamentary hearing that Japan has suspended flights of Ospreys until details of the crash and safety are confirmed.

The US-made Osprey is a hybrid aircraft that takes off and lands like a helicopter but can rotate its propellers forward and cruise much faster, like an airplane, during flight.

Ministry officials said a planned training flight on Thursday at the Metabaru army camp in the Saga prefecture in southern Japan has been cancelled as part of the grounding of all 14 Japanese-owned Ospreys deployed at Japan’s Ground Self-Defence Force bases.

A Japanese coastguard helicopter and patrol vessel conduct a search and rescue operation
A Japanese coastguard helicopter and patrol vessel conduct a search and rescue operation (Kyodo News via AP)

Japan has also asked the US military to fly Ospreys deployed in Japan only after “their safety is confirmed” except for the purpose of joining the ongoing search and rescue operations at the crash site, chief cabinet secretary Hirokzu Matsuno told reporters.

One US Osprey has joined the rescue operation since the crash, Japanese defence officials said.

The US Osprey crashed on Wednesday off Japan’s southern coast, killing at least one of the eight crew members. The cause of the crash and the status of the seven others on board were not immediately known.

The coastguard, as well as Japanese troops, searched through the night, and on Thursday the coastguard started using sonar to search underwater for the broken aircraft which might have sunk to the sea bottom, at a depth of about 100 feet.

Ospreys have had a number of crashes, including in Japan, where they are used at US and Japanese military bases. In Okinawa, where about half of the 50,000 American troops are based, governor Denny Tamaki had said he would ask the US military to suspend all Osprey flights in Japan.

Japanese coastguard spokesman Kazuo Ogawa said the coastguard got an emergency call on Wednesday afternoon from a fishing boat near the crash site off Yakushima, an island south of Kagoshima on the southern main island of Kyushu.

Coastguard aircraft and patrol boats found one male crew member, who was later pronounced dead by a doctor, Mr Ogawa said. They also found debris believed to be from the aircraft and an empty inflatable life raft about half a mile off the eastern coast of Yakushima, he said.

A Japanese coastguard escort ship, bottom, helps in the search and rescue operation
A Japanese coastguard escort ship, bottom, helps in the search and rescue operation (Kyodo News via AP)

NHK public television and other news outlets reported that the aircraft had requested an emergency landing at the Yakushima airport about five minutes before it was lost from radar.

NHK quoted a Yakushima resident as saying he saw the aircraft turn upside down, with fire coming from one of its engines, and then an explosion before it fell into the sea.

Defence ministry officials on Thursday refused to confirm the sequence of events or witness account, citing discussions with the US side.

US Air Force Special Operations Command said the CV-22B Osprey was from Yokota Air Base and assigned to the 353rd Special Operations Wing.

Ogawa said the aircraft had departed from the US Marine Corps Air Station Iwakuni in Yamaguchi prefecture and crashed on its way to Kadena Air Base on Okinawa.

Yokota Air Base is home to US Forces Japan and the Fifth Air Force. Six CV-22 Ospreys have been deployed at Yokota, including the one that crashed.

Last year, Air Force Special Operations Command ordered a temporary stand-down of its Osprey fleet following back-to-back safety incidents where the Osprey clutch slipped, causing an uneven distribution of power to its rotors.

The marine corps and navy have reported similar clutch slips, and each service has worked to address the issue in their aircraft, however clutch failure was also cited in a 2022 fatal US marine corps Osprey crash that killed five.

According to the investigation of that crash, “dual hard clutch engagement” led to engine failure.

Separately, a US marine corps Osprey with 23 marines aboard crashed on a northern Australian island in August, killing three marines and critically injuring at least five others who were taking part in a multinational training exercise.