[Japanese Defense Ministry will investigate the cause of missing ground self-Defense Force helicopter] April 20, according to the Japan Broadcasting Association, Japan's Defense Ministry said on the same day that the ground self-Defense Force helicopter that crashed before was equipped with a flight recorder capable of withstanding high water pressure, and the cause of the accident will be investigated after salvaging the airframe. At around 16:33 that day, a Japanese Land self-Defense Force helicopter suddenly disappeared from radar while flying near Miyako Island, Okinawa Prefecture, with a total of 10 people on board, Japan's Ministry of Defense said.