Pilot error led to an MV-22B Osprey crashing in shallow water off Okinawa nearly nine months ago, Corps officials said.

On Dec. 13, one of the Osprey’s propellers hit a refueling basket and host during a regularly scheduled training mission, according to an official investigation.

The pilots decided to conduct a water landing rather than trying to fly the stricken aircraft over a populated area, according to an announcement Sunday from III Marine Expeditionary Force.

Corps officials said the investigation determined that pilot error caused the crash, but Corps officials have not released a copy of the investigation despite a pending Freedom of Information Act Request by Marine Corps Times.

“This was a regrettable incident but one that could have been much worse without the quick reaction of the crew and the support of our Okinawan and Air Force partners,” Lt. Gen. Lawrence Nicholson, III MEF commander, said in a news release. “We will continue safe flight operations of the MV-22 and all of our aircraft in support of our alliance with Japan.”

With advances in aircraft design, construction and maintenance, the vast majority of crashes these days are caused by pilot error, said retired Navy Cmdr. Chris Harmer, senior naval analyst at the Institute for the Study of War.

“With that said, what this finding leaves out is that reduced flight time and limited training opportunities are a direct contributing cause of pilot error,” Harmer told Marine Corps Times on Monday.

“Pilots who do not get sufficient, dedicated flight time in a realistic training environment are far more likely to cause pilot error induced mishaps. Individual pilots can only be as proficient as their training and readiness budget allows them to be.”

Marine aviation has been struggling for years to keep pilots flying amid deep budget cuts, shortages of spare parts, aging aircraft and delays in new planes and helicopters.

Since March, the Department of Defense has prevented the Marine Corps and other services from telling reporters how many hours pilots are flying each month to avoid publicly disclosing readiness problems.

Following the Dec. 13, crash, the Marine Corps suspended all MV-22B flight operations in Japan for a week.

“It is very important for Japanese citizens to understand and share our utmost confidence in the safety and reliability of the MV-22, or we would not continue flight operations,” Nicholson said in a Dec. 19 statement. “It is equally important that we ensure our pilots have every opportunity to conduct training, which allows us to remain proficient, and enable us to respond when most needed in support of the alliance.”

But Okinawans have expressed concern about having Ospreys based out of Marine Corps Air Station Futenma, near the town of Ginowan. Opposition to having Ospreys next to a populated area has also become intertwined the efforts by Okinawans to get all U.S. troops to leave the island.

The “good news” in III MEF’s Sunday news release is that the MV-22B crew prevented any deaths of Okinawa civilians by risking their lives to put the Osprey down in the water, said Jeffrey Hornung, a political scientist at the RAND Corporation, who specializes in Japanese security issues.

“Despite the fact that proper training prevented a bad situation from becoming a deadly one, I still think this statement will be received negatively in Okinawa, where the focus most likely will be on the ever-present danger Futenma poses to the surrounding community, with particular attention paid to the safety of Ospreys,” Hornung said on Monday.