This decision came in response to a tragic incident one week prior, where a tiltrotor aircraft crashed off Japan's coast, resulting in the loss of eight lives.
AP News reported that the Air Force, Navy, and Marine Corps grounded hundreds of Osprey aircraft after a preliminary investigation into last week's crash found a possible mechanical issue.
"Preliminary investigation information indicates a potential materiel failure caused the mishap, but the underlying cause of the failure is unknown at this time," Lt. Gen. Tony Bauernfeind, head of Air Force Special Operations Command, said in a statement.
Last week's crash occurred on Wednesday, about 2 miles from Yakushima island. This area is part of Japan's Kagoshima prefecture and about 650 miles southwest of Tokyo.
A prolonged grounding might create a 'preparedness' issue for the military:
"If the Osprey grounding keeps going for a week or more, the inconvenience starts to become something more. And without the Osprey, training can be affected, and that affects readiness," Grant Newsham, a retired U.S. Marine Corps colonel and research fellow at the Japan Forum for Strategic Studies, told Reuters.
At least 50 individuals have lost their lives in either operating or testing the Osprey, which has earned the nickname "widow-maker."