Japan grounded its fleet of V-22 Osprey planes last Sunday after one of its hybrid helicopter planes unexpectedly tilted during takeoff and crashed into the ground.

The V-22 was taking part in the joint US military exercise Keen Sword and was carrying 16 passengers, including three US soldiers. During takeoff “it became unstable, swinging from side to side, and the left wing, the lower part of the aircraft, came into contact with the ground and part of the aircraft was damaged, so the flight was cancelled.” In the statement made by the Self-Defense Forces, the following statements were made:

It was the first major incident for Japan’s V-22 fleet since the Osprey crash last November, which killed eight Air Force Special Operations Command personnel and grounded the entire fleet for months in both Japan and the United States.

The aircraft resumed flight operations earlier this year, but the Osprey’s use remains controversial, especially in Okinawa, where residents have questioned its safety records.

Defense Minister Gen. Nakatani told reporters last week that the Osprey managed to land in last Sunday’s incident and no one was injured, but that Japan would keep its fleet of more than a dozen V-22s grounded while it investigated the incident.

“Although ensuring flight safety is a prerequisite for aircraft operations, we believe there are no safety issues at Ospreys,” Nakatani said.