TOKYO — Japan’s fleet of hybrid-helicopter military aircraft has received authorization to recommence operations after being grounded due to an incident that occurred last month.

On October 27, a V-22 Osprey experienced instability during takeoff and made contact with the ground while participating in a joint exercise with the U.S. military. Subsequent investigations revealed that human error was a contributing factor in this event.

The aircraft was carrying a total of 16 individuals when it “became unstable” during takeoff at a military facility located on Yonaguni, a secluded island situated to the west of Okinawa. Fortunately, the takeoff was aborted, and no injuries were reported, according to statements from Japan’s Ground Self Defense Forces (GSDF).

In an announcement issued on Thursday, the GSDF stated that the pilots had neglected to activate a switch intended to temporarily boost engine output during takeoff, which led to the aircraft performing an unstable descent and swaying unpredictably.

Chief Cabinet Secretary Yoshimasa Hayashi indicated that an internal review established that the accident stemmed from human error and was not attributed to “physical or external factors.”

He further elaborated that the fleet, consisting of more than a dozen V-22 aircraft, would be allowed to resume flight operations starting Thursday, following a thorough examination of safety protocols and training practices.

This incident marks the first significant event involving Japan’s V-22 fleet since a crash off the southern coast of Japan in November 2023, which resulted in the loss of eight lives during a U.S. Air Force Special Operations Command operation.

Although the fleet had just resumed its flight activities earlier this year, the deployment of the V-22 remains a contentious issue, especially in Okinawa, where local residents have raised concerns regarding its safety record. This southern island is currently home to around half of the approximately 50,000 U.S. military personnel stationed in Japan.