(CNN)A US Navy plane crashed into the ocean southeast of Okinawa on Wednesday afternoon, marking at least the sixth apparent accident involving a Navy asset in East Asian waters this year.
Plane crash latest in spate of US Navy accidents in Asia since January
The C2-A Greyhound transport plane was carrying 11 crew and passengers to an aircraft carrier when it crashed into the Philippine Sea, the Navy said. As of Wednesday evening, eight people had been rescued, and three were missing.
Wednesday's crash comes three weeks after a Navy and civilian panel recommended sweeping changes in a comprehensive review of the Japan-based US 7th Fleet, which covers East Asian waters.
The review found that two deadly accidents -- the collisions of the USS Fitzgerald and the USS John S. McCain with commercial ships in June and August, respectively -- were avoidable.
The review's recommendations include new processes for scheduling ships; "ready for sea" assessments for all Japan-based ships; disseminating lessons learned form "near misses"; and ensuring that ships routinely transmit on their automatic identification systems to prevent collisions.
Of the six incidents, Wednesday's is the only one directly involving a Navy aircraft. The others are collisions involving US warships.
The following are the details of the six incidents:
The Navy says the C2-A Greyhound transport was headed from a Marine Corps base in Japan to the USS Ronald Reagan when it crashed Wednesday in the Philippine Sea, about 500 nautical miles southeast of Okinawa, Japan.
The cause of the crash wasn't immediately known, the Navy said.
Japanese Defense Minister Itsunori Onodera told reporters Wednesday that the US military told him that engine trouble might have caused (the crash)."
The aircraft belongs to a Japan-based squadron that generally flies cargo and passengers between shore bases and the Reagan.
On Saturday, a Japanese tugboat lost propulsion and drifted into the USS Benfold in a bay off central Japan, causing minor damage to the guided-missile destroyer, the Navy said.
No one was injured. An investigation is underway.
The Benfold and the tugboat were participating in a scheduled towing exercise when the accident happened, the Navy said.
The Benfold was able to remain at sea; the tugboat was towed by another vessel to a Japanese port.
The USS John S. McCain, a Navy guided-missile destroyer, collided with the oil tanker Alnic MC about 50 nautical miles east of Singapore on August 21.
The collision left 10 US sailors dead. The McCain sustained significant hull damage, with flooding in berthing compartments as well as machinery and communication rooms.
Two days after this -- which at the time was the year's fourth collision involving a US warship in East Asian waters -- the Navy relieved Vice Adm. Joseph Aucoin of his duty as the US 7th Fleet's commander, citing a "loss of confidence in his ability to command."
Shortly before the collision, according to the November report, the McCain's commanding officer ordered a watch team to divide the duties of steering and the speed control of the ship after noticing one of the sailors on deck was having some difficulty at the controls.
The report says this shift created confusion among the team, and after steering control of the ship was transferred to a different control station, members of the crew failed to recognize the change in configuration.
The McCain was now in a heavily congested maritime environment and was soon on a course to collide with the Alnic MC, an approximately 30,000-ton and 600-foot-long oil and chemical tanker.
The report says the commanding officer and others on the ship's bridge "lost situational awareness" and did not register the course and speed of the approaching tanker. The McCain collided with the tanker after crossing in front of its bow.
Among the lapses highlighted by the report: The ships leadership failed to assign sufficiently experienced officers to certain duties; other senior officers failed to attend a security briefing the afternoon before the collision designed to provide awareness of the risks involved in upcoming operations; and some of the sailors were insufficiently proficient with the ship's systems.
The McCain's commanding officer and executive officer were relieved of duty after the accident.
The USS Fitzgerald collided with the container ship MC Crystal off the coast of Japan on June 17, resulting in the deaths of seven US sailors.
The bow of the cargo ship tore a hole in the Fitzgerald's side. The Navy provided a harrowing account of US sailors attempting to escape a rapidly flooding sleeping area.
Of the 35 sailors in the sleeping area at the time of the collision, 28 were able to escape, but the remaining seven sailors died.
November's report found that the Fitzgerald's officer of the deck realized too late that the Fitzgerald was on a collision course with the Crystal.
The Crystal also failed to take action, the Navy said, but the military still holds itself at fault for failing to avoid the collision.
"The officer of the deck, the person responsible for safe navigation of the ship, exhibited poor seamanship by failing to maneuver as required, failing to sound the danger signal and failing to attempt to contact Crystal on bridge-to-bridge radio," November's report reads. "In addition, the officer of the deck did not call the commanding officer as appropriate and prescribed by Navy procedures to allow him to exercise more senior oversight and judgment of the situation."
The report details similar failures by other crew members.
It cites failures to: plan for safety; adhere to sound navigation practice; execute basic watch-standing practices; properly use available navigation tools; and respond deliberately and effectively to an emergency.
The Fitzgerald's commanding officer, executive officer and senior noncommissioned officer were removed from their duties after the collision.
In May, a South Korean fishing boat struck the USS Lake Champlain, while the Navy warship was conducting operations in international waters near the Korean Peninsula, the Navy said. No injuries were reported.
The 60- to 70-foot-long fishing vessel collided with the Lake Champlain -- a 568-foot Ticonderoga-class guided missile cruiser that has been with the aircraft carrier USS Carl Vinson strike group.
The fishing vessel crew later said it didn't have a radio and didn't hear the radio calls from the Navy, according to a Navy official.
Though these waters generally are the US 7th Fleet's responsibility, the Lake Champlain and the USS Carl Vinson strike group belong to the 3rd Fleet.
In late January, the guided-missile cruiser USS Antietam ran aground while trying to anchor in Tokyo Bay.
The ship damaged its propellers and spilled hydraulic oil into the water off the coast of Japan.
The incident did not result in any injuries to US or Japanese personnel, but the discharge of up to 1,100 gallons of hydraulic oil prompted environmental concerns.