The Super Cobra crashed on May 5 in the Cleveland National Forest.
The aircraft was inspected at the El Centro Naval Air Facility that day, according to Marine officials. A mechanic only partially secured the transmission cowling because he thought the chopper would be grounded overnight.
Instead, the pilot, Capt. Jessica Conkling, flew back to Marine Corps Air Station Miramar. She and 1st Lt. Aaron Cox didn't tell mechanics making another repair about the cover, which came off in flight. Both died.
The crash victims, who were originally from Marine Light Attack Helicopter Squadron 267, Marine Aircraft Group 39, which was based at Camp Pendleton, were assigned to fly with Marine Medium Helicopter Squadron 166 (Reinforced) as they trained for an upcoming deployment. They were on a night-time training exercise at the time of their deaths. The aircraft's wreckage ignited a brush fire that was still smoking hours later.