An F/A-18D Hornet conducts an aerial refuel. U.S. Marine Corps photo by Gunnery Sgt. Christopher Giannetti

The Marine Corps has finally finished investigating a midair collision off the coast of Japan that killed six Marines in December.

The collision of an F/A-18D Hornet and KC-130J Hercules occurred when an inexperienced fighter pilot conducted an unusual maneuver, lost situational awareness, and hit the back end of the tanker aircraft during nighttime refueling operations.

But there were other issues, as the investigation also called attention to the unprofessional command climate within the fighter squadron, which was characterized by the misuse and abuse of prescription medications, a disregard for safety, and a number of other serious problems.

In the wake of the incident, the commanding officer, the executive officer, the operations officer, and the aviation safety officer were all relieved of their duties.

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Six Marines lost their lives in a tragic midair collision last December, and an investigation has revealed a number of serious problems that caused the unfortunate incident.

In the pre-dawn hours on December 6, 2018, an F/A-18 D Hornet collided with a KC-130J Hercules aerial refueling tanker during an air-to-air refueling mission, sending both aircraft crashing into the sea.

The fighter jet, one of two involved in the refueling operation, was from Marine All-Weather Fighter Attack Squadron 242, or VMFA(AW)-242, and the tanker aircraft was with Marine Aerial Refueler Transport Squadron 152 (VMGR-152). Both squadrons are part of the 1st Marine Aircraft Wing, the aviation combat element of III Marine Expeditionary Force.

During the routine refueling operation, the lead fighter refueled and moved into position on the right side of the tanker. After the second of the two Hornets completed refueling, the pilot, who was unfamiliar with nighttime air-to-air refueling, made an unusual request to move into a non-standard position on left side of the tanker, and that is where everything went wrong.

"The investigation indicates the mishap pilot lost situational awareness, unintentionally crossed over the top of the KC-130J from left to right, and collided with the rear of the tanker," the Marine Corps said in a statement Monday.

The six Marines who perished in the collision were Capt. Jahmar F. Resilard, a 28-year-old F/A-18 pilot, and the crew of the KC-130J: Lt. Col. Kevin R. Herrmann, 38, Maj. James M. Brophy, 36, Staff Sgt. Maximo A. Flores, 27, Cpl. Daniel E. Baker, 21, and Cpl. William C. Ross, 21.

Read more: These are the 6 Marines who died when a fighter jet collided with a refueling tanker off the coast of Japan

The oldest member had served in the Marine Corps for 16 years. Three were married, two with children.

After looking into the matter, the Marines concluded that there were no mechanical or technical problems with the aircraft involved in the collision.

The investigation did, however, identify several problems that contributed to the accident, including but not limited to an unprofessional command climate, inadequate oversight of training and operations by squadron leadership, service members who were not medically fit for duty, and a lack of proficiency on the part of the fighter pilot.

Evidence surfaced of VMFA(AW)-242 officers engaging in prescription drug seeking behavior, the wrongful use of prescription and over-the-counter drugs, excessive alcohol consumption, adultery, the assignment of sexually explicit call signs, order violations, and failures to uphold the fundamental principles of professional aviation training and operations, the investigation revealed.

A toxicology report found that two of the individuals involved in the mishap had Ambien and over-the-counter cold medication in their urine, indicating that they were not fit to fly.

"The squadron command climate created nonchalant attitudes towards safety and standardization, which contributed to the mishap by fostering an atmosphere where ad hoc, unscheduled flight schedule changes were not properly authorized, planned for, and executed," the Marine Corps investigation read.

"The pre-flight brief of 5 December 2018 was truncated to a point of irrelevance. Overall, VMFA(A W)-242's planning and preparation ... was conducted in a confused and dangerous fashion with an almost willful disregard for basic risk management practices."

The investigation notes that the December 6, 2018 incident is disconcertingly similar to an incident in April 2016 in which an F/ A-18D from VMFA(AW)-242 Hornet collided with a KC-1301 from VMGR-152, shearing off the refueling hose and drogue. Both aircraft suffered damage, but the incident was not fatal.

"The information gathered during the investigation led the Commanding General of 1st Marine Aircraft Wing to lose trust and confidence in the leadership of VMFA(AW)-242," the Corps said in a statement. The commanding officer, the executive officer, the operations officer, and the aviation safety officer were all relieved of their duties.

"We must all learn from these failures and not repeat them," Lt. Gen. H. Stacy Clardy, commander of III Marine Expeditionary Force, said in response to the findings of the investigation.

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