SAN DIEGO (AP) — An aviation training accident that killed seven Marines — one of the Corps’ deadliest aviation training accidents in years — left the military community shaken and was a solemn reminder that preparing for war poses some of the same risks as the real thing.

“It’s an unfortunate consequence of the high tempo of operations,” said retired Marine Col. J.F. Joseph, an aviation safety consultant. “They’re out there working on the edge trying to exploit the maximum capabilities of the aircraft and their tactics. Just by the virtue of that, in becoming combat ready, these unfortunately are not uncommon occurrences.”

The Marine Corps and Navy, nonetheless, stand out in their efforts to mitigate that risk and make training as safe as possible, he said.

Officials said it could take weeks to determine what caused two helicopters, an AH- 1W Cobra and a UH- 1 Huey, to crash in midair during a routine exercise Wednesday night, killing all aboard the aircraft. Skies were clear and the weather was mild.

The accident occurred near the Chocolate Mountains along the California-Arizona border — a sprawling desert range favored by the U.S. military because its craggy mountains and hot, dusty conditions are similar to Afghanistan’s harsh environment.

With 17,500 Marines and sailors, including personnel stationed at Camp Pendleton and Marine Corps Air Station Yuma in Arizona, the 3rd Marine Aircraft Wing conducts hundreds of aviation training exercises a year so troops can get as much experience as possible before they go to war.

It was the fifth aviation accident since March involving the 3rd Marine Aircraft Wing headquartered at Miramar Marine Corps Air Station in San Diego. Throughout the Navy and Marine Corps, there have only been two other aviation training accidents in the past five years involving seven or more deaths, according to the military’s Naval Safety Center.

Chaplains and counselors were called in to talk to troops. Six of the Marines killed were from Pendleton — the West Coast’s largest base — and one was from the base in Yuma.

The Marine Corps won’t release their names until their families have all been notified. A Fresno man said his son was among the dead.

James Everett told the Fresno Bee that his 33- year- old son, Sgt. Justin Avery Everett, was a 10-year Marine Corps veteran who served two tours in Iraq and was scheduled to go to Afghanistan in July.

He grew up in Fresno and he was a wrestler at Reedley High School. Justin Everett is survived by his wife, a 5-yearold daughter and a 2-year-old son who live in the Winchester area of Riverside County, James Everett said.

Gov. Jerry Brown issued a statement on behalf of himself and his wife: “Anne and I offer our condolences to the families and friends of the Marines who died last night. We honor their bravery and sacrifice.”

Two of the Marines were aboard the AH-1W Cobra and the rest were in the UH- 1 Huey utility helicopter. They were flying in a remote section of the 1.2-million-acre Yuma Training Range Complex as part of a two- week standard training called “Scorpion Fire” that involved a squadron of about 450 troops from the 3rd Marine Aircraft Wing.

The helicopters collided near dunes at the edge of the Yuma range about an hour before the range was to shut down for the evening. Ground troops were in the area, but they were not affected, said Gunnery Sgt. Dustin Dunk, a spokesman at the Yuma base, which is a 90- minute drive from the accident site.

Part of the exercise involved having helicopters low on fuel descend to ground troops that have set up a refueling outpost, Dunk said.

He did not know if that’s what the pilots were doing at the time of the crash.

“ Our training is always evolving, safety is paramount, and being prepared is paramount,” he said. “It was a very standard exercise for what we do. Our thoughts and prayers go out to the family members. … Our investigation will look to see what went wrong and how to correct it.”

The AH-1W carries a pilot and gunner and is considered the Marine Corps’ main attack helicopter. The UH-1Y, which is replacing the aging version of the Huey utility helicopter first used during the Vietnam War, carries one or two pilots, a crew chief and other crew members, depending on the mission.