WASHINGTON (Kyodo) -- The U.S. military on Friday began requiring its Osprey aircraft to undergo an additional safety inspection following a recent precautionary landing involving one of the transport planes, but said those meeting the standard can resume flights.

The Naval Air Systems Command said it has ordered the inspection of the military's V-22 Osprey variants to verify the flight hours on each proprotor gearbox before the next flight.

In August, following a months-long probe, the military said a U.S. Osprey aircraft crash in November 2023 in southwestern Japan that killed all eight personnel aboard was caused by a proprotor gearbox failure.

The command said operations of Ospreys with such gearboxes under a certain number of flight hours will continue to be controlled, while those meeting or surpassing a predetermined flight-hour threshold will resume flights.

Citing operational security concerns, it did not disclose the details of the latest safety guidelines, including the number of Ospreys affected and how many hours are designated for the threshold.

"The V-22 plays an integral role in supporting our nation's defense. Returning these vital assets to flight is critical to supporting our nation's interests," it said in a statement.

The command also said it is committed to the safety of all Osprey operations, promising to monitor necessary data to provide the most reliable aircraft to service members.

Ospreys -- which take off and land like helicopters but can fly like planes due to their tilt rotors -- have a history of accidents and the fatal crash in Japan was the deadliest involving the U.S.-made aircraft.

Last week, U.S. forces said they had again temporarily grounded all their V-22 Osprey variants due to safety issues.

"A near crash" involving the aircraft happened on Nov. 20 at Cannon Air Force Base in New Mexico. It had similarities to the deadly incident which occurred during a routine exercise off the coast of Japan, according to The Associated Press.