The incident took place Wednesday morning when a CH-53E Super Stallion's window landed on Futenma Daini Elementary School's sports field, adjacent to the Marine Corps Air Station Futenma's fence line. At the time, there were 50 children on the field. One boy suffered a minor injury.
This is the second time this month an object believed to be from a US military aircraft fell on an Okinawan school. A transparent container with dark red label reading: "Flight," "US," "remove" and "use to reset" printed in English landed on the roof of a daycare in Ginowan, southern Okinawa, December 7. In October, a Super Stallion helicopter made an emergency landing in a field outside the Okinawa training area because of an inflight fire.
In a statement released Monday after an investigation was completed, the First Marine Aircraft Wing (MAW) claimed that the incident was caused by human error. The window, which was designed to be removed by a crew member in case of an emergency, was not properly secured before takeoff.
According to Marine officials, air and maintenance crews have undergone additional training since the incident. In addition, the helicopters have been checked for mechanical or structural issues related to the windows.
"1st MAW has taken comprehensive actions to ensure the safety of all Okinawa-based CH-53E aircraft, the aircrew that fly in them and our broader community," the statement reads. "This incident is regrettable, and we again apologize for the anxiety it has caused the community."
Marine officials will also conduct routine maintenance on their aircraft and commit to monthly safety meetings.
On Monday, Japanese Defense Minister Itsunori Onodera said that he was waiting for sufficient security measures to be established by the US military.
"Safety can only be ensured when all possible measures are taken to prevent reoccurrence," he said.
Japanese Chief Cabinet Secretary Yoshihide Suga has urged the US to avoid flying planes over hospitals and schools near Futenma, the Japan Times reported. However, the US military has already resumed its flights.
Okinawa Governor Takeshi Onaga called the US military's resumption of CH-53E flights following the incident "truly ridiculous" and has also said that the military is "not a good neighbor." Onodera said that the Japanese government has"not received a sufficient explanation about US measures to prevent a repeat" of such accidents.
Tomoko Miyagi, who was taking her 12-year-old son to school when the window fell out, said that the US military decision to restarts flights so soon is "unforgivable" and shows "contempt for the people of Okinawa."