TOKYO, Jan. 18 (Xinhua) -- The Japanese government lodged a protest with the U.S. military Thursday over U.S. military helicopters flying above an elementary school in Okinawa again, after a U.S. CH-53E chopper dropped a window on the school about a month ago.

At a press briefing on the matter, Japan's top government spokesperson described the flying-over incident in Japan's southernmost prefecture as deplorable and said the government would take action.

"It's extremely deplorable this kind of incident happened even though we're strongly demanding that the U.S. side not fly above the school," Chief Cabinet Secretary Yoshihide Suga told reporters.

The U.S. military, amid rising fears and indignation among the people of Okinawa owing to the increasing frequency of military-linked accidents and mishaps, had said that it would try to avoid flying its helicopters above the school.